Theoretically, you can shoot anything over anything. Whether it'll stick or not or whether it'll ever cure up properly is something you find out later, usually much to your chagrin. You can mitigate both of those things by using a "barrier" coat of shellac, but you'll end up with a pretty thick finish by the time you're done. Contrary to internet dogma, that won't affect the sound of an electric guitar, but what are you saving? In the grand scheme of things, you won't save any money but at least you're adding work and ending up with a half-assed job.
The people most likely to refinish are those who've never done it before. It's kinda like deciding to change the muffler on your car. Looks easy enough, and getting someone else to do it is always expensive even though the parts aren't. Seems like a no-brainer if you've got the time and ambition. So, you go to your trusty auto parts dealer and buy a muffler, and take it home to show everybody what kind of neat tricks you're capable of pulling off. Then mean ol' Mr. Reality shows up to piss in your cornflakes... :laughing7: