I have new knowledge to contribute to the hivemind.
For stripping acrylic paint off metal models in SECONDS I use methylene chloride.
CAUTION/WARNING/DANGER/PELIGRO: Methylene chloride is THE most toxic material suggested in this thread so far. The use of methylene chloride should only be undertaken with proper respiratory, eye, hand, and skin protection. Make sure the material does not come in contact with your bare skin. Ever. (It's carcinogenic, folks)
Anyway, they used to sell the stuff as "acrylic cement," for gluing big blocks of solid acrylic together. A guy I knew that used to own a game store suggested it, and after a few DROPS I could see bare metal. It works really quick! You'll have to use a metal or glass container to hold your subject since, like acetone, the chemical eats through plastic cups (I haven't tried paper, actually. Huh). You really don't need much, either. Because, you know. It's terrible for the environment and stuff.
[gmod]New info, it can stay[/gmod]