I'm not familiar with the idea of an amil-postmil would believe.
A lot of modern postmils are amil in the sense that they believe the Millennium began in the first century with Christ's (i.e. the God-Man's) Kingdom. But unlike proper amils, they believe that the Bible teaches that the Kingdom will make progress until it fills the whole Earth, and all nations as nations will acknowledge Christ as Lord and Saviour.
Some of the older postmils tended to indicate that the Millennium would start at some point in the future such that e.g.
(a) I believe, the Devil was bound in the future for many older postmils.
Amils and postmil-amils believe that the Devil was bound in the first century as mentioned in the Gospels. I tend to take from Revelation 20 and subsequent history that the Devil's binding started in the first century but hasn't yet reached its full extent.
(b)I believe, the first symbolical or spiritual resurrection was in the future for many older postmils.
Amils and postmil-amils believe that this started in the first century with people being resurrected to newness of life in Christ, with Christians (including those to be martyred) reigning on Earth with Christ, and with Christians (including those martyred) reigning in Heaven with Christ. Beheading was a common means of execution for the first century martyrs e.g. the Apostle Paul. It is a resurrection that includes both Earth and Heaven, as it happens for the individual on earth when they are regenerated, and when they go to Heaven (through martyrdom or otherwise) Christ says that in fact they never die, because rather than experiencing the Second Death, physical death for believers is just a transition to a higher state of life and reigning with Christ.
E.g. Jesus said unto her, I am the resurrection, and the life: he that believeth in me, though he were dead, yet shall he live: And whosoever liveth and believeth in me shall never die. Believest thou this? (John 11:25-26, KJV)
Postmillennial indicators in the Revelation 20 passage itself
v.1 The angel coming down from Heaven (Christ Himself, Who is often likened to an anonymous angel Who is yet involved in history in Revelation) has the great chain of the Gospel. According to the Evangelists the binding of Satan began while Christ was on Earth and was indicated by the casting out of demons.
vv.2-3 Satan is progressively limited in his power as the Gospel goes forth, until he is limited as much as he can be in this world.
v.4 "I saw thrones, and they sat upon them, and judgment was given unto them" indicates a reversal of "fortunes" for the martyrs and their Christian successors on Earth. As it were the souls of the martyrs reign upon Earth, as they have been vindicated by the course of history which has gone in the Christian direction. While the souls of the martyrs reign in Heaven, the Christian successors of the martyrs reign on Earth, not only spiritually but in reality, because the Devil has been fully bound and Christianity has become the dominant worldview.
Daniel 7 is relevant here:-
As I looked, thrones were placed, and the Ancient of days took his seat; his clothing was white as snow, and the hair of his head like pure wool; his throne was fiery flames; its wheels were burning fire. A stream of fire issued and came out from before him; a thousand thousands served him, and ten thousand times ten thousand stood before him; the court sat in judgment, and the books were opened. I looked then because of the sound of the great words that the horn was speaking. And as I looked, the beast was killed, and its body destroyed and given over to be burned with fire. As for the rest of the beasts, their dominion was taken away, but their lives were prolonged for a season and a time. I saw in the night visions, and behold, with the clouds of heaven there came one like a son of man, and he came to the Ancient of Days and was presented before him. And to him was given dominion and glory and a kingdom, that all peoples, nations, and languages should serve him; his dominion is an everlasting dominion, which shall not pass away, and his kingdom one that shall not be destroyed. As for me, Daniel, my spirit within me was anxious, and the visions of my head alarmed me. (Daniel 7:9-15)
v.8 mentions
Gog and Magog.
Ezekiel 34 to 39 is an extended "commentary" on Revelation 20, with a massive resurrection of God's people, a period of peace for Israel (Jews and Gentiles who believe) under David (Christ) in the Land (the whole world is God's Land of Israel in the New Covenant), followed by the attack by God's enemies associated with the names of Gog and Magog. I believe this fits the postmil scheme best.
See Patrick Fairbairn's excellent commentary on
Ezekiel.