Been using Simple Green for years and swear by it.
- Use a hose with a nozzle turned on jet and spray off each wheel.
- Hit each wheel with Simple Green (3 or 4 sprays)
- Use a dedicated sponge (because it gets really dirty and you don't want it on your paint) and scrub off the brake dust/grime. It should come off pretty easy.
- Rinse off the wheel and redo any missed spots with the sponge.
I usually do the wheels first then wash the rest of the car. Cheers.