For light scratches I've had good results with a product from Mequire's called PlastX.
Yes. and Maguires Mirror Glaze cleaner for heavier scratches. You can also go by the local Fixed Base Operator (FBO) at your local General Aviation Airport and see what they have for use on light aircraft windscreens (plexiglass/lexan). Their mechanics may be able to give you some tips on polishing out the scratches.
My top was scratched bad. I used a 220 grit to smooth it out and worked up to 1000 grit and then polished it out with a 3M rubbing compound and finally a polish. This took hours it does not polish fast. The process is alot like buffing paint only the material is alot tuffer so the results are slower. If the scratches are fine, start with a high grit and go higher. The higher the grit the faster the buffing will be or just use a high speed buffer and compound first to see if you can skip the sanding. Do not stay in one spot to long because of heat and do not use harse cleaners on it. Soapy water works fine.