I understand your pain.
Even though Poppy's hair wasn't as long as some other people's yorkies, it was still long enough to get really matted when wearing a coat or jumper.
She hates being brushed too so I tend not to put clothes on her unless it is really cold outside. Last weekend I took her to the beach and it was freezing so she had to wear a jumper. I took the jumper off her when we got home and her chest was just one huge matt, I tried to brush it out but the brush would only go through the top of the matt and wouldn't go anywhere near the rest of it.
She had her hair cut on Tuesday and I got her cut really short, so now she can wear clothes and she dosn't need to be brushed.
I hear you can get silk harnesses and silk lined clothing for babies with long coats which don't matt half as much or maybe not at all!