I'm also a fan of the Christensen products. Here is a link to their website:
http://www.chrissystems.com/
A couple of suggestions... Be sure you are *thoroughly* rinsing - shampoo or conditioner left in will attract dirt and oils much faster. Also, are you using hand lotion? You may be accidentally leaving some of that on his coat when you pet him. Last, CC has a product called "Final Rinse Solution" - it may help.