On our M235i I found that when using a wheel coating designed for resisting dirt/brake dust the brake dust still gets caked on, but is super easy to remove using just water. Whereas without the coating I needed wheel cleaners, soap, water, ect..
here is a blog we wrote on applying the coating to the Zito ZS01's that are on our M235
http://www.watershedautocare.com/blo...-wheel-armour/