I use a silver wide toothed comb. I have seen the ones with two widths. I have also had luck with the undercoat rake I use on my German Shepherds. I have to be really carefull with it though.

I just spent the afternoon removing matts and getting my arm 'gnawed' on. *sigh* At least he looks and feels better. But I found a couple more matts that I have to remove within the next couple of days before they get bigger.