Well presented how-to: refinishing wheels
 

I stumbled on this, and thought I'd seen it here before, but my search turned up nothing, so I'll post the link. I've used Wurth personally and find their spray paint the absolute best in the rattle-can department (and their wheel silver the closest match to MB too). :)
http://www.bmwtips.com/tipsntricks/wheel-repair/wheel-scuff-repair.htm