there have been several threads recently on this topic, with lots of pics. consensus is a paint pen, but it can leave a subtle choppiness to the line. some like using a pinstriping brush, with long, fine hairs. my only experience with this sort of thing as been with pinstriping cars, where i used an actual brush and slow-drying paint formulated for pinstriping. the trick is to keep a continuous, slow motion. i would imagine that maintaining that motion around the curvature of the lugs would be more challenging, and a paint pen would be far easier.