Well, Darwin no longer has mattted fur on his back.
Yesterday while he was eatting I started scratching his back. I noted that he was too busy chowing down to take a swipe at me with his claws or bite.
So, on a whim I grabbed a scissor and gently cut the mat off. Now Darwin has a bald sport on his back where the mat used to be. But it will grow back.
If Darwin had let me groom him, he wouldn't have the problem in the first place.
I might use feeding time to give him a couple of soft strokes with the brush so he'll get used to being touched and groomed. That's Darwin's real problem. He's been ferral so long he's not used to and doesn't like to be touched. That can be overcome....