The Night of the Demons remake is on YouTube right now.
The "scenes of interest" are in part 4:
7:00 has one of the female characters turn into a demon while having sex with her infected boyfriend. You don't get to have a good look at her full demon form until later in the movie (basically, she gets green skin and tentacle hair).
9:00 has Angela turn into a demon (no process).
No real process with the third demon-possessed female character. She gets her face ripped off and reappears as a skeleton-faced demon a few scenes later.
There. Now you don't have to watch the whole movie.