I don't use masking tape, it takes too much and is a nuisance and rarely wants to stick to the tire. Instead I brush paint the tires with straight dishwash detergent - its thick enough not to puddle at the rim and doesn't matter if it dries. I paint the rims then wash the detergent off when I'm satisfied the paint has dried long enough. If there is any minor seepage of paint through the soap it will come off easily with lacquer thinner. Oh, I do this with the wheels OFF the car and laying flat!