I had a nasty looking red plastic tank on a red bike that had many many coats of nasty red paint. Nothing I did would last. So I stripped all the paint off and found that someone had cut out zebra stripes ( probably from masking tape) into the plastic with a razor blade. These razor thin lines were black from years of dirt. So I used a buffing wheel to get the plastic to shine like new, and those very thin ghost lines looked extremely cool, many compliments. The plastic would dull from time to time, but three minutes with the buffing wheel and back to shiney red. Good luck with sanding, but I would use a buffing wheel.