Auto body repair & detailing: paint and repair of plastic fender on Firebird, dual action sander, light duty

Question
I am painting fenders on a 95 Firebird that came out of a u pull it lot.  There are some deep scratches.  Do these need to be filled the same way as any scratches on the metal parts of the car?

Answer
Do this- Sand the scratches out with 150-180 grit on a dual action sander. Blow clean with  air, while wiping with a clean towel. Apply a coat of USC Icing, P.N. 26006. It's a light duty skim coat filler. Apply it thin, give it a good half hour to set up, then sand. This will work just fine for what you are working on, and won't break the bank, or be hard to contour. bill