Ive used them on showcars. You will have to redo them every few car washes though, and they are not tire coating friendly. If you put it on over treated tires, it wont stick at all if you can even get it on. Threatments will remove, damage or miscolor them. I put it on tires that I never put anything on. I just clean my tires really well and leave them natural. I hate shiney or even semi-shiney tires.
Another thing that works just as well on clean untreated tires is just some white (or color) model paint with a little talcum or baby powder mixed in, and applied with a modeling paintbrush. That will make the enamel paint dry on the rubber. Still needs touch ups though, but looks much better. Works especially well on raised or outlined letters. You have to scrub them perfectly clean...any oils or dressings will leave oily smears in the paint. I bought a car with dressed tires and I spent prob 4 hours getting all the stuff off the rubber.
[This message has been edited by rogergarrison (edited 12-20-2013).]