During our winter this year, my Altima aluminum wheels looked very much like the BMWs wheel pictured. So before I took the car through the local car wash(YUP, the carwash), I gave the wheels a quick bucket of hot water mixed with "liquid" laundry detergent & another bucket of hot water rinse and, OMG, you had to see'em when I was done. And it only took me minutes to do all 4.
Now keep in mind, this laundry detergent cleanup isn't my regular way to clean the black brake dust wheels but the detergent sure did a nice job and better than many wheel specific wheel cleaning products that I've used in the past. I only did them quickly as well due to being cold outside and it was no work at all.