Do you have any recommendations on how acrylic paints can be used on plastic film?
Much will depend on the plastic being used. Certain plastics like HDPE2 (used for food containers and most of our paint jars) are very hard to get acrylic paints to stick well to. However, plastics like Plexiglas, Acrylite (both are acrylic plastics), Mylar and Polycarbonites, will accept acrylics very well. You may wish to increase the adhesion by blending with some GOLDEN GAC 200, a very hard acrylic medium, in with the softer paints (Heavy Body, Fluid Acrylics, etc..). It's best to test the paints on the plastic you intend to use, and clean the plastic well with a cleaner or rubbing alcohol.