Novus is awesome! I bought the 1 2 and 3 but I always find myself just using 2 on everything plastic. You can't beat Novus #2. If it's REALLY deep #3 then followed by #2 but get out a can of elbow grease. It goes further that way than using a buffer.
I used a car headlight scratch/cloudiness remover on a drill for some REALLY deep scratches in a Punch Out bezel (somebody scrached a * across the entire screen)... it worked really well considering how bad it was, though it didn't take it out completely.