I too, have one who matts easily with that cotton coat. That and her playing with the Min Pin pup..the Min Pin thinks it's cute to grab a mouthful of hair. NOT. Still working on manners with him as he's only 4 months old.
I have heard there is a product that is sold for horse manes that really helps. I've tried Miracle Groom...doesn't work well. I know where I can horse grooming supplies here..at the local Farm King...so am thinking a store that carries grooming products for horses.
I'll let you know how that works when I get it this weekend.
And yes, my brother had a Yorkie in Ariz. and he always had her clipped into a shorter style...to keep her cooler.
sadielyn