:whs:
Meguiar's APC (the green stuff) seems to do a good job at cleaning brake dust off wheels that have a solid build up.
As they're painted, you'll find that even most harsh wheel cleaners are quite safe on the wheel finish, although that can't be guaranteed for the parts behind it like the brake calipers and such- it may stain them.
If claying doesn't touch that residue, then maybe you'd want to try a bug and tar remover first before moving to a harsher wheel cleaning chemical. Also, do you have any stiffer/ denser wheel cleaning brushes other than the EZ Detail brush?
Meguiar's Wheel Brightener is extremely strong, and I believe the Poorboys one is too (although never used it).