Originally Posted by: pureim going to paint on my white plastic pick guard
hopefully with an airbrush
but i dont know what paint to use on my white plastic pick guard

Lemme ask you a couple things and be honest as hell. I'll explain the reasons below.
A. Do you have all the tools & paints to do the job AND know how to use them?
B. Have you ever stripped your guitar apart down to the pickups and put it back together including a setup?
C. Can you afford to buy a second pickguard if the one you work on gets messed up?
D. Can you live with a messed up paintjob?

Here's the real deal. If you answer NO to any one of these questions besides D, you might want to leave your guitar alone. The reason is that you can't do a good job without taking the pickguard off the guitar and stripping the electronics off of it. Yes you can try and mask off the pickups & electronics, but you run the risk of getting solvents & paints in there. When that happens, you might have to replace gummed up parts. (expensive)

You said "hopefully with an airbrush"... this leads me to belive that you A: don't have one, or: B, you have one and are not sure how to use it. If A happens to be true, you might as well save yourself some cash and buy a pre-decorated pickguard. Even a cheap airbrush kit will run you 50 bucks, plus the cost of a compressor. If B is the case, then you should practice your artwork on something cheap untill you get it right. Then go for the pickguard.

[edit] I read about your airbrush.... you might just want to buy a few more cans of air for it unless you plan on using it all the time. A good compressor isn't cheap... forget the ones made for 'hobby' use, they don't last. [edit]
BTW, PPG auto paint is NOT good for plastic, the solvents in it will eat through the stuff in about half a heartbeat. It's also insanely expensive for a project like this.

An alternative to airbrushing might be to use stencils & cans of spraypaint. Testor's / Modelmaster paint at the hobbyshop is a decent choice. The difference is that the paint drops in spraypaint are huge compared to an airbrush. If you don't do it right, the finish can come out real 'grainy' looking. Of course this all depends on what kind of paintjob you want on there. Doing a single color or even two isn't tough. If you ever built a model car and put some decals on it, you might be good to go.