Can you post a photo? Not sure if by dingy you mean it just means in need of thorough cleaning and maybe a bit of Flitz (of Maas or Gunbrite) to polish it, or if it is scuffed up and needs more rigorous attention?
Bolt appearance is often spruced up by jeweling it. You need an indexing fixture and a drill press for that. Brownells sells fixtures and the engine turning brushes and abrasive to create the surface texture, but that's a lot of investment for just one bolt. I'd have a gunsmith do it for just one.
You can strip it and buff it, then polish it if scratches need to be removed, but if they are longitudinal scuffs from the bolt way, then they will come back if you don't clean up the inside of the way.