just painted my 04 matte white. i tried to clean her but was unsuccessful. so i went to a car wash that washes my brother in laws car, he has 3 matte black cars. and they do an amazing job. but i dont want to have to drive all the way out there when she gets dirty. and she gets dirty! its been raining a lot and this color is like a dirt magnet.

pointers?
good shampoos?
good technique?
all help is appreciated. thanks guys.