Scottrt
XS650 Addict
When painting mag wheels with the machined outer rib face I use a light film of axle grease on the surface I don't want the paint on... this serves as the masking (or more accurately as a release agent). As long as you don't go apeshit with the spay patern/thicknes it is easy to come back the next day and wipe of the grease/paint and have a crisp line. I did this to a CB1100F I used to own and it made the job much quicker.