If ya paid small bux for it, its a worthy project.
I reckon strip it right back to a bare playfield and seriously buy a top quality airbrush kit and learn yourself (thats what i am aiming to do).
If anything Wotto, you have nothing to lose by practicing on other bits of wood, then once u are okay with the airbrush, give that playfield ago.
Either way mate, I love ya passion, and I reckon determination will get u there in the end. More challenge, more fun when you win in the end. Keep us updated.