The best way to keep black and dark colors clean is to use a premium polymer wax system to seal the car . I use KLASSE A German Polymer wax that is a 2 step system One is a cleaner and prepares the surface for the sealer. This system actually puts a fine protective film that may protect your car from fine chip damage. I put this on every 6 months and in between use a fine Carnuba detailer . As for dirt all you do is hose the car off with water and it is gone. My wife has a dark Blue that is out all the time and You can't believe that she does not wash it every day because the car looks like it was just waxed. It is the best wax system on the market today if you are looking for a good polymer protection and shine. I would suggest you try www.aandmmotorsport.com They specilize in car care, MUGEN and other Honda performance parts. But their car care section is great and you can drop them a line if you have any questions.