Matt 3:
11 I indeed baptize you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and with fire:

Let's continue looking at verse 11.
"but he that cometh after me is mightier than I"

"he that cometh"
2064 erchomai (er'-khom-ahee);
middle voice of a primary verb (used only in the present and imperfect tenses, the others being supplied by a kindred [middle voice] eleuthomai (el-yoo'-thom-ahee); or [active] eltho (el'-tho); which do not otherwise occur);
to come or go (in a great variety of applications, literally and figuratively):
KJV-- accompany, appear, bring, come, enter, fall out, go, grow, X light, X next, pass, resort, be set.

2064 erchomai-
1) to come; used of persons:
1) to come from one place to another, and used both of persons arriving
2) to appear, make one's appearance, to come before the public
2) metaphorically:
a) to come into being, to arise, to come forth, to show itself, to find place or influence
b) to be established, to become known, to come (fall) into or unto
3) to go, to follow one

"mightier"
2478 ischuros (is-khoo-ros');
from 2479; forcible (literally or figuratively):
KJV-- boisterous, mighty (-ier), powerful, strong (-er, man), valiant.
2479 ischus (is-khoos');
from a derivative of is (force; compare eschon, a form of 2192); forcefulness (literally or figuratively):
KJV-- ability, might ([-ily]), power, strength.
2192 echo (ekh'-o);
including an alternate form scheo (skheh'-o); used in certain tenses only); a primary verb; to hold (used in very various applications, literally or figuratively, direct or remote; such as possessions; ability, contiuity, relation, or condition):
KJV-- be (able, X hold, possessed with), accompany, + begin to amend, can (+-not), X conceive, count, diseased, do + eat, + enjoy, + fear, following, have, hold, keep, + lack, + go to law, lie, + must needs, + of necessity, + need, next, + recover, + reign, + rest, + return, X sick, take for, + tremble, + uncircumcised, use.

2478 ischuros-
1) strong, mighty
a) used of living beings
1) strong either in body or in mind
2) used of one who has the strength of soul to sustain the attacks of Satan, strong and therefore exhibiting many excellences
b) used of inanimate things:
strong, violent, forcibly uttered, firm, sure
2479 ischus-
1) ability, force, strength, might
2192 echo-
1) to have, that is, to hold;
to have (hold) in the hand, in the sense of wearing, to have (hold) possession of the mind (refers to alarm, agitating emotions, etc.), to hold fast keep, to have or comprise or involve, to regard or consider or hold as
2) to have, that is, to own, to possess
a) external things such as pertain to property or riches or furniture or utensils or goods or food, etc.
b) used of those joined to anyone by the bonds of natural blood or marriage or friendship or duty or law, etc., of attendance or companionship
3) to hold oneself or find oneself so and so, to be in such-and-such a condition
4) to hold oneself to a thing, to lay hold of a thing, to adhere or cling to, to be closely joined to a person or a thing

"whose shoes I am not worthy to bear"

"worthy"
2425 hikanos (hik-an-os');
from hiko [hikano or hikneomai, akin to 2240] (to arrive); competent (as if coming in season), i.e. ample (in amount) or fit (in character):
KJV-- able, + content, enough, good, great, large, long (while), many, meet, much, security, sore, sufficient, worthy.
2240 heko (hay'-ko);
a primary verb; to arrive, i.e. be present (literally or figuratively):
KJV-- come.

2425 hikanos-
sufficient
a) many enough, enough
b) sufficient in ability, that is, meet, fit
2240 heko-
1) to have come, have arrived, be present
2) metaphorically
a) to come to one, that is, to seek an intimacy with one, to become his follower: to come upon one (unexpectedly)
b) to come upon one, used of things endured

"bear"
941 bastazo (bas-tad'-zo);
perhaps remotely derived from the base of 939 (through the idea of removal); to lift, literally or figuratively (endure, declare, sustain, receive, etc.):
KJV-- bear, carry, take up.
939 basis (bas'-ece); from baino (to walk); a pace ("base"), i.e. (by implication) the foot:
KJV-- foot.

941 bastazo-
1) to take up with the hands
2) to take up in order to carry or bear, to put upon oneself something to be carried, to bear what is burdensome
3) to bear, to carry
a) to carry on one's person
b) to sustain, that is, to uphold, to support
4) to bear away, to carry off
939 basis-
1) a stepping, a walking
2) that with which one steps, the foot

Flesh men's bodies are made from the elements of the earth, in other words, "dirt".
John is saying that he, within himself, as this dirt, is not even fit enough for YAHSHUA'S feet to walk upon....not fit
enough, within himself, for The Word to be carried forth.
Yet, through YAHSHUA, and because of CHRIST, The Anointed One, we each can become a worthy bit of the
earth that can be utilized to bring forth HIS WORD, THE LIVING WORD, YAHSHUA, JESUS CHRIST.
We can become clean spiritually through repentance and baptism, and therefore become fit servants for HIS use.

John continues to bring forth that which each should understand about YAHSHUA, JESUS CHRIST.

"he shall baptize you with the Holy Ghost, and with fire"
The baptism, that YAHSHUA shall place upon HIS servants, shall not be only the cleansing of the flesh man of his
sins, but the total cleansing and preparation of the servant's spirit and soul.
Each vessel (servant) must be cleansed by HIS fire in order to become fit for HIS HOLY SPIRIT to be poured into.
This "fire" is as lightning, and refers to HIS Sword...Word of Truth.

Acts 2:1-4
1 And when the day of Pentecost was fully come, they were all with one accord in one place.
2 And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting.
3 And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
4 And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance. (KJV)

Is the 'sealing' the same event as the 'baptism of fire'?
No, one must first be cleansed, then 'sealed' in order to then be "baptize with the Holy Ghost, and with fire".

Acts 2:1
1 And when the day of Pentecost was fully come, they were all with one accord in one place. (KJV)

In other words, these were all sealed and of one accord.

2 Cor 1:21-22
21 Now he which stablisheth us with you in Christ, and hath anointed us, is God;
22 Who hath also sealed us, and given the earnest of the Spirit in our hearts. (KJV)

"sealed"
4972 sphragizo (sfrag-id'-zo);
from 4973; to stamp (with a signet or private mark) for security or preservation (literally or figuratively); by implication, to keep secret, to attest:
KJV-- (set a, set to) seal up, stop.
4973 sphragis (sfrag-ece');
probably strengthened from 5420; a signet (as fencing in or protecting from misappropriation); by implication, the stamp impressed (as a mark of privacy, or genuineness), literally or figuratively:
KJV-- seal.
5420 phrasso (fras'-so);
apparently a strengthening form of the base of 5424; to fence or inclose, i.e. (specifically) to block up (figuratively, to silence):
KJV-- stop.
5424 phren (frane);
probably from an obsolete phrao (to rein in or curb; compare 5420); the midrif (as a partition of the body), i.e. (figuratively and by implication, of sympathy) the feelings (or sensitive nature; by extension [also in the plural] the mind or cognitive faculties):
KJV-- understanding.

4972 sphragizo-
to set a seal upon, to mark with a seal, to seal
a) for security: from Satan
b) since things sealed up are concealed (as the contents of a letter), to hide, keep in silence, keep secret
c) in order to mark a person or a thing
1) to set a mark upon by the impress of a seal or a stamp
2) angels are said to be sealed by God
d) in order to prove, to confirm, or to attest a thing, to confirm authenticate, to place beyond doubt
1) used of a written document
2) to prove one's testimony to a person that he is what he professes to be
4973 sphragis-
a seal:
a) the seal placed upon books
b) a signet ring
c) the inscription or impression made by a seal; used of the name of God and Christ stamped upon their foreheads
d) that by which anything is confirmed, proved, authenticated, as by a seal (a token or proof)
5420 phrasso-
1) to fence in, to block up, to stop up, to close up
2) to put to silence
5424 phren-
1) the midriff or diaphragm, the parts of the heart
2) the mind; the faculty of perceiving and judging