Originally Posted by babymog

The problem is that the deposits are usually harder than the paint, so buffing will remove more paint than deposits.

Wet-sanding might be an option, but attacking it with a mild acid (such as vinegar) is probably going to be the least damaging. I'd even consider something stronger such as Tile-X or other acidic product, just try it on paint where it won't be seen first, and DON'T LEAVE IT ON!!! Rinse thoroughly and often if you find an acid that will work.

The darker the color, the more likely that the acid will make the paint blush.