A few months ago I decided for the first time to remove my wheels for a quick clean and seal. It didn't take long to realise this is something I should have done before I allowed the brake dust to build up. Mazda MPS wheels having 10 spokes it is always difficult cleaning the base of the wheel. This is what I discovered.
BEFORE

Heavy Duty Degreaser diluted 4:1 was my only option available. You hear of some professionals using acid, however this was not something I was comfortable with for a few obvious reasons.
After a lot of effort this was the end result.

Far from perfect but a marked improvement nevertheless. Prima Wheel Armour was then applied to prevent this for happening again in the near future. Wheel Armour is a great product for the fact that application is effortless. A simple wipe on, wipe off product that cleans and seals in the one application.
The product wipes on clear and dries to a haze in about 30 secs like the following picture

The residue buffs off very easy to produce the following finish.

For maintenance I recommend cleaning the brake dust off "dry". A quick wipe with a cloth reveals the brake dust that has coated the wheel has not actually bonded with the surface and the sealant is doing its job. Cleaning when wet I found turned the dust into what can best be described as "sludge" which takes slightly more effort to remove.