I've noticed that most people are finishing and polishing their picks using
sandpaper. That's one way to do it, but there is a rubberized abrasive
material called cratex. You can get it from various places that sell machine
tools and shop tools.
The material feels like rubber, comes in different grades. It comes in sticks, bars,
and mounted on 1/8" shafts that can go into a tool. Great for polishing stuff, removing
light rust, etc.
I would use the sandpaper to do the rough stuff but cratex to do the polishing.