To remove chrome plating from brass - you first need to be sure it is chrome plating on brass - you use hydrochloric acid. This is, I believe, still known by it's old name of muriatic acid in some parts of the world.
It is really nasty stuff and obviously you'd need to completely strip the camera down and treat ONLY the chrome parts.
This is possible with simple folding cameras and cameras where you can easily remove, say, a chrome top plate. I can't see it as being feasible with a complex SLR. If you did manage to strip it down and just have the body parts by themselves - I would give them to a pro plating company and get them to strip and re-plate it for you. I've done this with motorbike bits before and it isn't so difficult to get done or so expensive - it is stripping the camera down this far (and putting back together!) that would be completely out of the question IMHO.