Depends on the level of scratches. You can sand them all down with the common sense method of coarse grit all the way down to super fine grit like 1500 wet, or what I did since I have built RC Planes and have a heat gun is use the heat gun to bring the color back to plastic to make stress marks and small scratches fade away. When I used my heat gun, it basically made everything besides gouges go away. A hot hair dryer at a closer range would probably work as well, but would take longer.