I have not tried it but someone told me of a trick when trying to paint rims with the tires mounted. Get a cheap deck of cards and fan them out around the edge of the rim between the back of the rim and the front of the tire. You could then easily cover the rest of the tire.
I wonder how many deck of cards is needed for this painting process? I would love to see a pic of the pre-painted "deck of cards" wheel!
