Painting plastic trim

SEM is good stuff but pricey! You can get "Bulldog" adhesion promoter fairly cheap at most auto parts. Clean substrate real good with soapy water and scuff it with 1000 wet sandpaper. I never had to apply any primer when using the Bulldog. Painted a set of my 3 wheeler fenders with auto paint and it has been stuck for 6 years, no peeling yet!