Just take them apart, it's not overly difficult. Definitely remove them from the bike, you don't want overspray getting all over. I've done many sets but I don't use rattle can so can't comment on how it would hold up to brake fluid getting all over it. My guess is it would mess it up pretty quick. I've done some with automotive paints but I usually just powdercoat them. Remove the pads, remove the cylinders, don't lose the little black rubber washers either. Take them to your powdercoater and tell him to mask off the inside where the cylinders go and around threaded areas and you're good to go. Then just hand letter the Brembo. This topic has been covered before about lettering. Someone said you could use a potato with paint on it and do it that way too.