Wet sand with automotive grits starting at around 400 then 600, onto 800 then 1200 or 1500... If you can find 2000, then do it too. Start by going perpendicular to the scratch, and for each successive grit, go perpendicular to the direction of your last grit as well as feathering out the edge of your area. Then use a product by 3m for polishing automotive urethane clearcoats called Imperial Hand Glaze and apply it like this: Put a bit on to a rag; for a large scratched area, use a mechanical buffing wheel, like an orbital sander wrapped in the rag... Single scratch/small area, the tip of your finger inside of the rag is good. Use a little bit, because what happens is the stuff gets better as it gets drier from the friction. You want to rub it till it squeaks like a clean dish. Polishing acrylic has to do with HEAT HEAT HEAT so the faster/harder you rub, the quicker your results will come due to the friction. Flame polishing can warp/craze/stress-crack acrylic fast, and isn't necessary on a surface scratch, as it is really meant for polishing edges. Hope this helps!