I've done this once. If you don't have a sandblaster it's not worth the effort. You'll need rough sandpaper to get the labels off, fine sandpaper to make it smooth and steel wool for polish. Then you end up with keys which look like they've been in heavy use since 1999, so you'd need a sandblaster to get that fine grain on the key surface, at which point you could just as well have used a sandblaster from the start.
I hear rip/ster has one, maybe if you send him a picture of yourself with a keyboard on your head, he'll do it for you.