Painting plastic trim

You can clean the parts with something like Scuff Stuff http://www.prestaproducts.com/Scuff_Stuff__Surface_Prep-details.aspx

Then use an adhesion promoter bull dog is good and comes in spray cans or quarts

x3 on the bulldog spray can, worth the 10 bucks. used it for plastic bumpers, motorcycle parts with great results.