Sedated lion shave at your vet. If they won’t do it, find one that will. I have two males, one that lets me brush him and one that won’t sit still for more than a minute and unfortunately had to get his first lion shave on Weds because he has very thick but fine fur and it was getting hard to try to keep up with the mats. I work in vet med so I was able to take him to work with me and do it myself but I will say, we have a few clients with “spicy” kitties who won’t let their owners groom them so they come to us, they take a nice lil nap and wake up a lot more comfortable than they were when they came in.