frank- yep. have been working with automotive coatings for over 20 yrs, and in the custom field for 15 or so.
gan- urethanes. dupont chroma clear series.
plabonte- yep, although additional layers of coatings can have effects on tonal integrity.
the factory coatings on some guitars are epoxies, and very tough to remove, although, some manufacturers use urethanes, which are easier to remove.
if you wanted some airbrush work, and a clearcoat protectant, i would not worrie about the change in your sound.
howevre, if we were to change the color of the piece altogether, especially to a kandy or other color requiring multiple coats, and not remove the factory layers, the resonance of the substrate could be affected, although, most i've come across become slightly more tinny, at best.
something that appeals some guitarists, and also something only you, and your tech might notice. nothing substantial.
e-mail me with any questions.
[email protected]
blacky