Our large breed long hair rescue despises being groomed. We've had him 9m and he had a tough start in life, I just don't think he's used to it.
He's starting to like it round his chops, but anywhere that actually needs it is a no-no. I'm constantly covered in scratches, bites and bunny kick bruises from trying to get him used to it. He makes such a racket too, like the cat equivalent of crocodile tears
We have had a groomer come in, but even she didn't get much done, and he drew blood. In the end he was muzzled and he still got the muzzle off in his rage 
The groomer recommended a wide tooth comb, as regular brushes and the mitts do jack-shit for his lugs and thick coat. It works if I can get near him
Any suggestions please, my hands and arms can't take it anymore?!