More tips and notes:
We say that the Wheely Clean, when used without agitation or a wheel brush will clean about 80% of the grime away on dirty wheels when used with a pressure washer. Now this is with road grime, which usually comes if you have driven in rain and the like. Also, the first time you clean a really dirty wheel (especially inners) it could be a lot less, so you will need to use some agitation or wheel brushes to help the Wheel Clean out. After this initial clean, if it's just brake dust, it will clean closer to 95% of it off when used with a good pressure washer. We strongly recommend that you continually clean your wheels or a regular (weekly) basis to keep it working this way.
For a 100% clean, use a good soft bristle wheel brush (like Wheel Woolies - dip it in some water before use), especially for the heavier built up areas, like the inner wheel. It only takes an extra minute to do and is worth the minimal effort used.