In the past, I have let the air out and collapsed the tire off the bead and lay news paper in the bead area all the way around. Front and rear. Paint and after drying, remove the paper and air them up. Just my 2 1/2 cents
The easiest way I’ve found to paint a rim; get an old deck of cards and place them tucked between the rim and tire one by one and over lapping, all the way around the wheel. Spray paint and move on. It’s really very fast and you can use the cards many times.
By the time you do that, you can take of the tyre!
