Thanks. Those would be tough letters to paint, they are so small. When I do paint tire letters I first clean the tires by scrubbing with kitchen cleanser. The paint I find easiest to use is reefer white Floquil lacquer. It's a bit of an off-white color, just like real white letters. I've got tires I lettered using this that are 20 or more years old and none of them have yellowed. Or not enough to notice.