Pretty much anything but chances are, you'll need to sand the finish until it's somewhat rough and apply a metal primer so that it bonds properly.
I used automotive paint for mine. I sanded the interior down with 180 to strip the finish, then used 320 to take the rough grit off, and finally with 800 to smooth it out. I then laid down two coats of high-build primer to cover minor scratches, sanded that down with 1200, and applied a few coats of paint. I then applied several coats of high-durability clear coat.
The problem with doing that is that the paint will make the overall thickness of the panels slightly larger, which can cause problems when you try to put it back together.
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