The excellent fledgling blog Christocentricism has a post taking the summaries of Johnathan Edwards' answer to the question "In what sense did the saints under the old testament believe in Christ to justification?".
You can find the full Edwards' answer here, starting at 372 (note, there's a lot of stuff there).
Here are the overviews of the 11 points:
I. The person that in Jeremiah 2:2 and in many other places is spoken of as espousing that people Israel to himself, and that went before them in the wilderness, and brought ‘em into Canaan, and dwelt amongst them in the Holy of Holies in the tabernacle and temple, was the Son of God, as is most manifest by that, that he is often called the “angel of the Lord,” “the angel of God’s presence,” “the messenger of the covenant,” etc.
II. It was plainly and fully revealed to the church of Israel that this person was a different person from him in heaven that sustained the dignity and maintained the rights of the Godhead, and acted as first and head and chief in the affairs of God’s kingdom; and that this person, that had espoused the church of Israel to himself and dwelt amongst them as their spiritual husband, acted under him as a messenger from him. And as this was sufficiently revealed to that people, so the church of Israel all along understood it.
III. One of the names by which that divine person, that was with the Jews in the wilderness and that dwelt with them in the land of Canaan, was known among them, was “the son of God.”
IV. The church of Israel understood that this person which has been spoken of had united himself to them in the strictest union, and had espoused them and become their spiritual head and husband, and had most nearly interested himself in their affairs.
V. The church of Israel had it plainly signified to ‘em that God, the first person in the deity, had committed them to the care and charge of this angel of his presence, that he had set him over them to be in a peculiar manner their protector, guide and Savior, and head of their communication and supplies, and God’s people trusted in him as such.
VI. The people of Israel could not but understand that this person was transcendently dear to God, i.e. to the first person in the deity.
VII. The saints in Israel looked on this person as their Mediator, through whom they had acceptance with God in heaven and the forgiveness of their sins, and trusted in him as such.
VIII. The saints in Israel were led to that apprehension, that their prayers and all the sacrifices which were offered in the temple were accepted, and that God was reconciled to those [that] worshipped and made their offerings there, as though atonement were made and a sweet savor offered. Not on account of the value of their offerings as in themselves, but through that person called God’s name who dwelt there as their Mediator, and through his worthiness.
IX. God’s people of old must needs understand that that divine person that had espoused that people, and that formerly went before ‘em in the wilderness and dwelt among them as their Lord, protector, Mediator and Redeemer, was he that was in future time come into the world in the human nature, who was the Messiah so often promised.
X. God’s saints in Israel supposed that the Messiah, when he came, or the angel of the covenant, when he should come to dwell amongst men in the human nature, would make an end of their sins and wholly abolish the guilt of then by an atonement which he should make; and that the guilt of their sins, though removed from them and as it were laid upon that divine person who dwelt on the propitiatory in the temple, and was by him taken on himself, yet would not properly [be] abolished and made an end [of] till he should come.
XI. The saints in Israel understood that the way that the Messiah was to make a proper and true atonement for sin, and make an end of it, was by his own suffering and by offering up himself a sacrifice for sin.
XII. God’s people brought and offered their sacrifices, depending upon them for reconciliation to God and acceptance to his favor, no otherwise than as representations of that great sacrifice and atonement of the Messiah, or as having reference and respect to that.
XIII. Such a dependence on the divine Mediator as has been spoken [of] was the revealed and known condition of peace and acceptance with God.
And thus I suppose the saints under the old testament trusted in Christ and were justified by faith in him.