I had the same problem. Used Simple Green and seems to work pretty good. I didn't spray the whole wheel, just sprayed some on a rag and wiped it down, then rinsed off the wheel.
In to see what people say! Coming from a srt charger i thought 6 pot calipers and brake dust were the death of me, these wheels seem to be just as deadly, especially after a fun weekend off-roading lol. The Matte black isnt so Matte and dirt doesn’t like to come off these.