There was just a whole thread on the Newf-L group about this. A Newf had been lost in a forest in Vancover(??) and when he was finally found had tons of pine pitch all over him. There were all sorts of suggestions: Pam (the kind you spray in cooking pans), peanut butter (gets chewing gum out of girl's hair; but that's a whole other story
), basically anything that has an oil will get sticky stuff out. If it is just dry mats, maybe try bathing him and using a creme rinse or conditioner??
If worse comes to worse, get a matt remover comb: the kind that has sharp teeth that will cut the mat in to pieces so it can be combed out without pain. It's something I use all the time on the Newfs and they tolerate it well. Good luck!!!