No matter what you do its going to chip, unless you ride nothing but the dunes. If your hellbent on painting them, just get the fusion paint that is the same color as the plastics now, so when they chip and scratch it wont be as noticable. As for prep, use a fine grit scotch brite pad and work the plastics over till there is no more shine. make sure the plastics are clean, dry, and oil free. As I said before it will chip, and scratch. And it will spider when the plastics flex to much. Thats why using the same color as the plastics already are is better.