Sounds like Jen has the best idea for this one. I use just a plain old comb for Peanut. She doesn't like any of the brushes that I have and one day I started with just the comb and she like it, so that's what we use. Tubby likes brushes, but he's not as much of a problem as Peanut with her longer hair. She gets the mats too, under her arms too - just like Noah. I use the "picking" action described by Jen to get it out. You will eventually loosen enough hair that the entire mat will just pull right out.

Good luck, and I envy you the 80 degree weather!!! We've got at least an inch of snow on the ground today and it's still coming down.