You also have to bulldog it first, that is an adhesion promoter, but before all of that you have to really clean it and sand it really really good. Spray the adhesive promoter on and then use a good quality primer like marhide or etching primer. than a good urethane based paint and have a way to bake it on. When you paint urethane body kits you have to paint it in a bake booth or the paint will just flake off like red stated under wind flex.
I always thought that it would be pretty cool to paint my plastics, but I have heard bad things about how the paint chips and cracks. I think you might be better off buying new plastics. Your going to end up spending the same amount of money on trying to paint when you could of bought some nice cheap plastics.