I want to mention that when you brush you should do it from the ends of the hair UP the same way you would long hair on a human. Work your way into the mat & then gently seperate it. Cornstarch (just a tiny bit) works to help loosen the mats too. Whatever you do, don't try to bathe your pup with mats present as this will really set the mat & then you'll have no choice but to cut it out.
Welcome to YT!