Maybe you could use hydrogen peroxide with a spray bottle and make him a reverse dalmation? Don;t know if that is safe or not. We used bluing at one kennel to brighten the whites. It is safe, but since your dog is dark, that won't work. I used bluing (u can even put it in bird baths says so on the label) to dye Victor blue for HAlloween. Wanted him to be Blue's Clue like the cartoon. He was blue, but nobody got my joke, oh well.