I looked into this after buying a second hand set of SSR 3 piece rims, I found out I had two choices..
1) get them diamond cut and lacquered by a pro.
2) take off what was left of the lacquer, flat them down with wet and dry paper, then polish up with autosol.
I went for option 2 in the end but months later really wished I had got them diamond cut and lacquered, the brake dust gets right into the join to the centre piece, there now all pitted and are a real pain to clean, not to mention polish back up, get them done buy a pro then it makes cleaning them easy and they will stay polished.