Here's my theory: Why clean them? They're just going to get dirty again.
Seriously. Does anyone remember the metal cleaner that came in a little, round metal tin, that had what looked like old furniture stuffing in it? It was saturated with something clear and it worked like magic. I don't recall any grit or abrasion occurring with cleaning - maybe letter removal. I'm not even sure it was made for cymbal use. Just curious.