I bought a black magic product that had about as much effect on brake dust as water did, so I triedd mineral spirits and one of those 3 m mesh type cloths that worked real well. anyone else use basic chemicals?
i think the trick was the fine mesh stuff, it really came off easily and had been on for a year or two since last washee- the pad used on flat top ceramic cooktops is about the same stuff as the green pad I got from a hardware store. the spray on black magic stuff had zero effect.
On a day with low enough humidity an upside down can of "canned air" for cleaning PCs can help with really stubborn stuff. I should say don't try it when your wheels/brakes are still hot from driving.