sometimes a slicker brush will work to seperate matts. Part the hair down to the skin and then work the slicker from the skin outward in little sections. It's kind of a pat and pull method, pet the brush into the base of the mat and gentle pull up and out. Follow up with the comb. A good conditioner might help and it might not, I personaly never have much luck with them but then most of the dog's I get are probably in much worse shape than dutch boy.
I'd say go slowly with the worst of the matts, Hopefuly they will be easy enough to work out of the coat.