Thanks for the replies! GM refers you to the owners manual and in the case of the ZR1 to the General Tech Bulletin we got with the car that says apply no chemicals to the brake rotors. I will use plain soap and water as they recommend, but when you have narrow spokes, it is hard to get in there. I like the idea of using a sponge paint brush. It will work great on the back (Plenty of clearance), but the front has barely 1/2 to 1 inch clearance from the wheel to the edge of the rotor so will be tight, but worth a try. I guess could have the dealer pull the front wheels off next service and clean them then. Appreciate the input.