Cleaning Tires (HELP)

My mom just got new American Racing rims on her 4runner and the dealer told me when i clean the tires ( with armorall and such ) NOT to get the cleaning solution on the rims because it would cause them to spot and bubble if i got too much on them.... and i swore that i saw on a website a circle guard that you can spray the TIRE but NOT the RIM. But i cannot remember where... so can someone tell me if there is actually such a thing and maybe where i can find it! THanks ALOT

I use a piece of cardboard that is cut to the wheel diameter ...