Here's a tip if your doing plastic parts such as dirt bikes.Sometimes getting paint to stick is kind of hit and miss sometimes. Get this,get a small propane torch and lightly waft it over the bare plastic. somehow this changes the molecular structure of the surface. Now apply your adhesion promotor as usual and carry on. Again it's an old trick,been around for awhile. By doing this the paint will stick like s*** to a blanket. Giver a try just don't do a true fire effect with the torch.