As long as the surface is smooth, it can be rub n' buffed! :thumbsup It basically is wax with a metallic tone added to it. I rub n' buffed my helmet and entire set of armor for my V1 Jango Fett and it had a great look to it, I recently upgraded to cold-cast armor to become screen accurate, otherwise I'd still have that same set of armor. But, yeah, it takes a little work to prep the surface working with finer and finer grades of sand paper, along with a choice of primer, for fiberglass I just went with Krylon Gray Primer. Hope that helps, I'll post some pictures tomorrow.
:cheers