When I painted my Noble Huna, I used some copper wire and stuck it into the hole in the stud connector that is on each '01/'02 mask. I also drilled a hole into the center of an axle so I could connect that to the wire as well as making the mask fit better on a Metru head. You could find another alternative to the copper wire and bend it, enabling you to paint the back. I don't have any images, but once I do, I can show you the method I used. Hope that helped.
Also, does anyone know a paint similar to Metallic Green?
And Chrome Green?