I've found auto products work pretty well - I have a white Brompton with a matte finish and a mountain bike with an off-white finish, so I feel your pain. For places where the surface has been mildly abraded I've found a slightly abrasive colour restorer works pretty well. We have a product called T-Cut over here which I've used for years, so even if you don't have that where you are you can probably look it up and find something similar. The other product I have which appears to be almost magic in it's abilities is Autoglym Super Resin polish. This not only appears to remove remove light scuffs but gives a lovely shine as well. Can also be used on cars!