The haze may be in th clear coat. Typically you will have a base coat (the colour, black) and then several layers of clear coat over top. If the clear coat has gotten scratched, rubbed, or abrased, you'll usually see white marks. Try to find a buffing compound and test it on a small, un-noticable area before doing the whole frame. The grit in the compound will almost *sand* away some of the damaged clear coat, and should smoothen things out, leaving a nice clean surface. Polish or wax afterwards too if you really want it to look nice
It's not paint... it's anodized black. And for this particular year, the aluminium finish is not smooth but grainy. Therefore, unless you rinse off using a reasonably high pressure washer or brush the metal, some of the dirt won't come off. I don't seem to have a problem cleaning mine off.