Other than the two citations, where does the info on these lesser known angels come from?
Selaphiel: the prayer of God, impelling to prayer (3 Ezdras 5:16). He prays to God for mankind.
Jehudiel: the glorifying of God, encouraging exertion for the glory of the Lord and interceding for the reward of efforts.
Barachiel: distributor of the blessings of God for good deeds, entreats the mercy of God for people.
Jeremiel: the raising up to God (3 Ezdras 4:36)
"Other than the two citations, where does the info on these lesser known angels come from?"
I suspect, but I don't know, that it comes from pious tradition in The Church.