Just as a general caveat: I think it's important to know what materials the case is made of. The metal part, of course, will stand up to punishment, but if there are any plastic piece that have been painted on it's very dangerous to apply any kind of solvents to these. There's a very real danger of melting the plastic pieces.
However, if you're removing paint from metal, I've got some suggestions. I've stripped paint using brake fluid, of all things. You can also try spray-on oven cleaner.
Both substances are toxic, of course, so prepare accordingly. Wear protective clothing and use a filter breath mask when using the spray-on oven cleaner.
I've got a couple more ideas, but the product names escape me at the moment. If they come to me, I'll post again later.
Hope this helps!