Don't have R90's.
I buy 5 litres of wheel cleaner at a time I find this far more cost effective. I've just bought Valetpro Bilberry Safe Wheel Cleaner, 5 litres cost me £28 including vat and delivery. Bilberry can be used neat or diluted with water upto 10:1, it is a very effective safe wheel cleaner.
Swissvax Wheel Brush to clean the face of the wheel and EZ Detail Brush to clean inside. To protect the wheels I use Chemical Guys Wheel Guard.
Here are the results I have achieved,
Front wheel

Rear wheel

