Here's a little trick I like to do. I got a 3 pack of different size drives that allow you to use sockets on your drill. Any hardware store should have these. Now you find the socket with the correct outer diameter, attach it to your drill and spin it on your pice of sandpaper on a flat surface. Reverse the and repeat until you get the desired effect. You can even angle the drill a bit if you like. For the sidewalls, I found that these plastic ice cream containers with a screw on lit works nicely when you put some sand in with your too new looking tire. Then shake until you are satisfied.