Another vote for
PB's WS. I have a summer and winter set of wheels and tires. Before each season, I clean the wheels very well and apply 3 coats of WS. I haven't had any problems with stubborn brake dust since and 3 coats seem to last the entire season. As a side note, I have been running a Stoptech big brake kit for the last two seasons. They produce a lot of extra heat and dust and the WS still holds up.