Try paint thinner or brush cleaner. I've had particular luck with brush cleaner. It removes pretty much everything. You may also wanna get some plastic polish just in case the plastic gets scratched or smudged (harsh chemicals may cause the plastic to soften a bit).
I assume it was the Testors enamel you used(they also have acrylic paint) For enamels use mineral spirits and rub off with a cloth or old toothbrush. If that does not work, I have a book that recommends using cellulose thinners. BUT, it is very hazardous without proper ventillation or a respirator. I have never used it and I am not sure where to get it, maybe a hardware or hobby store. Hope this helps
Don't use any of those harsh chemicals...Go to Home Depot and buy a can of denature alcohol...it works perfectly, with only a little effort, and WILL NOT DAMAGE the plastic at all...no hazing or scratching, like the other chemicals will do...denatured alcohol is only a couple of bucks for a quart or something...
i just bought blue batmobiles red out vinyl overlays and this post couldnt've come at a better time cuz i need to remove my sprayed out tails... i think im gonna try the denature alcohol and see how it works. thanks for the tips!!!
The easiest way to use the denatured alcohol, is to soak (I mean REALLY soak) a rag with it, and lay it on the painted area for about a minute. Pick up the rag, pour a little more alcohol on, and rub the paint off. It should just start peeling off, and will eventually just slide off the light. It depends on how long you let the soaked rag sit on the paint and loosen it from the plastic.
EDIT: Btw, the credit for using denature alcohol goes to Jesse IL...He told CloneGTS about it, who posted it in his write-up...