Anything that is a grease remover. Spray 409, Simple Green, Castrol Super Clean.

I find with plastic you can get away with just dishsoap and water....resin (especially the non mainstream stuff) need a little more "oomff" to get the release agent off.

As far as paint....once you get the parts squeaky clean. Shoot with a good primer, and paint as you would a regular styrene part.