Hello Kevin, I used the spray. Spray about three to four lite coats only giving them about 30 seconds to dry between the coats and removing the stencil or masking tape before it has a chance to dry much. If you wait too long everything will come off with the stencil. I found that the lettering will yellow over time, but I am fine with that. It has also held up well for me, but I don't have my cobra anymore and will be using this stuff on my RCR40 once it arrives.
You can get tire lettering stencils here:
http://www.racelinedigital.com/store/index.php?cPath=6