Hello I am new to the site and ran across this thread on painting plastics. They make a paint that is used for painting plastics a friend of mine owns a Plastic injection molding business that makes baits for Mister Twister, Zoom and some other big name companies. I buy paint from him that is used to paint plastics the key to this paint is the thinner. The thinner of the paint is the same chemical that is used in PVC pipe cleaner. When used on the baits it soaks it up into the plastic and will not come off. If you buy the purple PVC pipe cleaner and dip one of your baits into it you will see what I am talking about. I use a air brush gun and spray this paint on shad and other baits works very well and you can cut out a design like eyes, scales etc. in cardboard or card stock and lay over the bait when you spray and give a custom design.
Just thought I would add to this thread for what its worth..
Fish On !!