SEM does have "Plastic adhesion promoter" that can help with the peeling and lifting issue. Clearcoat is normally what protects paint from chips and scratches. I'd scuff the plastic parts with a 600grit scotch brite pad, spray it with the adhesion promoter, paint it, and clear it if you desire the glossy look. You could get all of that stuff from your local auto paint store, and not worry about paying for shipping. You can even take one of the interior trim pieces to the store and ask them how to prep and paint it. If you're not looking to spend a fortune doing this make sure you tell them so they don't just try to sell you on their most expensive stuff. Most paint stores have those SEM rattle can products.