I bought a used '94 miata in 2002. It had waterspots all over it, and no matter how hard I tried, I couldn't get them off. I washed, waxed, rewashed, waxed again, and nothing. I tried "cleaner" waxes, and no results. My neighbor had a 90 BMW, and the paint looked like new. She recommended I use Liquid Glass. Now, at first I was kinda sceptical cause it came in the same kind of can that turpentine/paint thinner come in, and it had a warning about containing petroleum distillates. But once I tried this stuff, WHOA!!! Water spots gone with almost no work. Just spread it on, waited a bit for it to dry, then buffed it off. After a few coats over about a month, some guy pointed out that my car had some dents in it. I wife replied with "What the hell do you expect? It's a 94" The dude came back with "You're ******' kidding me!! That paint looks new!" And it did. 'cept for the little dents. Then I took a Clay Bar to it, and re-applied the Liquid Glass. You could set a Buffing cloth on the hood, and it would just slide down the hood on it's own.
IMO, this was some really good s***!! It's not available to me now, cause I nobody in Alaska distributes it, and it can't be shipped up here. So that sucks. But the only place I ever found it at was Pep Boys. It's in a gold can with a red corvette stingray on the front. 17.99. Not cheap, but well worth it.