we use this stuff, its not cheap but one bottle has done at least 3 sets of wheels and all the plastics on 2 cars (twice)
it lasts for ages (12 months plus!!) and it really is just a case of a quick blast with the pressure washer and they come up clean or the slightest bit of rub if really really bad
http://www.ebay.co.uk/itm/CarPro-CQu...gAAOSwPc9W0gEQ