PM me if you have an interest in a take off grip safety, maybe a take off thumb safety or maybe even a take off bushing to use as test pieces. Grip safeties I recall with certainty are in good supply. They have flats and rounds like a slide.
I don't know what Colt uses, but if you want a mirror finish, use an 8000 grit stone. I use a Norton water stone, working up starting from 1000 grit.
BTW, you'll find the flats aren't actually flat when you start. Because of that, I assume they use a wheel or belt.