What is the best way to remove car paint oxidation?

I own a black eclipse which the paint has oxidized badly. When I first got it I had a sponge that took it off really easy but whenever it rains it comes back. I since then threw away the cheapo sponges thinking the local dollar general would still carry them. Nope. Iv'e since tried 2 other sponges a scrubbing pad which worked excellent but scratched the paint very easily and another that hardly had any effect. Any recomendations out there for sponges or products? Iv'e tried Nu-Finsh and didn't have good results. And unfortunately someone broke into my garage and stole my buffer. Thanks