Well I'm going to have to put my two cents in here, when my dad painted my 6-string bass we fiber glass resined the back of the neck then We masked off some flames, sprayed silver, then unmasked it and sprayed candy read over it...Looks amazing, the resin added alot for strength, the neck hasnt budged at all, i need to adjust the rod in it now cause of new string but before it was dead straight. But i would STRONGLY recommend against doing that over paint. Because the fiberglass would leave a rough texture on the neck and you would HAVE to clear coat it, thus building up more material.
Bass-man