I have used NU FINISH car polish for about 20 years now. Have used it on cars, trucks, boats, canoes, kayaks and even polished the plexiglass
windows and crome belly-band on the trailer. It's mild enough that it doesn't rub off the finish on painted surfaces but a good rubbing will take the small scratches off the plastic. It's available from CTC and a lot $cheaper$ than many big name brands.
I guess I sound like a commercial but it is one of the best I've found for the $buck$