Ahh yes, those Brembo pads throw a ton of dust, don't they?
I clean the entire wheel every wash, because they get very dirty after a week or so - I don't have to tell you. I spray down the entire wheel, inside and outside, with All Purpose Cleaner. You can use Green Wheel Cleaner too, it does the same job. Now for the All Purpose Cleaner, I just spray it on - I don't dilute it or anything. I'm not a freakin' chemist - I just want to spray the stuff and be done with it. Let it sit for a few seconds, then I use Adam's Boars Hair Brush and go to town on them. For the back wheels the Boar's Hair Brush fits no problem. On the fronts, I have to use this cheap Autozone brush to fit under the section of the wheel where the caliper takes up. Other than that one section, I use the Boars Hair Brush.
I hope that helped.