Recently I tried out the sanding/buffing combo, its pretty effective but wont be as shiny as brand new plastics. You have to sand from 220-1000 grit, 220 for deep scratches only, 400, 800, and wet sand with 1000. I don't recommend trying to buff the plastics by hand so your going to need a buffer, or a bit that attaches to a drill with a buffer pad on the end. You'll need a cutting compound, and a polishing compound. I didn't take any pictures after I finished, but it came out pretty good. In the end I just ended up scuffing my plastics back up and painted them.