I've never seen Raiders (sorry, not a fan of Mr. Spielberg, Lucas etc.). But you should definately see the Incredible Melting Man, The Devil's Rain and The Beyond for all 3 have juicy, gross melting effects that look a lot more convincing then stop motion. In fact , the first two films mentioned here are the granddaddies of cinematic ooze.

The melting wax sculpture method is what you are talking about and it is really old, and predates color movies.

Many of the vampire movies in general use that technique, also a movie called Blood Rain, if I remember right. There are too many to mention, as others have said, it is standard fare in the genre.

It was also used in at least one episode of the original star trek.

Tom Savini has a great discussion about the technique and walk through in one of his books.

By the way, in The Terror, the hot chick was not a witch, she was the victim of a witch out for revenge. She was a real girl posessed by the spirit of another woman who had died a long time prior.