I highly recommend a product from 3M called One Step Cleaner Wax - Medium Oxidation Remover. I purchased it online at 3M's online store as I couldn't find it anywhere locally. Try http://www.3m.com/US/auto_marine_aero/index.jhtml

I have a white 91 190E that when bought had a dull haze all over, stains and smears. It looked like the PO hadn't cleaned it in five years. You could rub your finger across the surface and white would come off on your finger - not good.

Anyway I went over the whole car with this stuff, its grunt work as you have to work small areas and rub firmly in and then wipe off with clean terry. But it worked magic, the dull finish and dead paint dissappeared, stains were gone, fine scratches around my door handles vanished. I followed with a coat of liquid wax.

It looks like a new car again - awesome stuff.

Doug