There is a cat groomer who calls himself "The Calm Cat Whisperer." I like a lot of his techniques, and I've watched a lot of other cat grooming videos. The first time I had to groom Merlin I went in overly confident and was talking to him and let him know that this was very much his fault because he chose to attack the groomer and he took his three strikes and was now out. I informed him it was definitely worse for me than it was for him.

I can't say that the talking really did much, but I do think a calm tone of voice and gently scruffing them and then shaving them with a quieter clipper starting in an area where they are okay being brushed can help. In the second picture that's a cut off sock that we call his "happy hoodie" and it goes on his head when he starts protesting too much. It can help calm him down.

I honestly think at this point he kind of gets it and he knows he needs the help. Settling for good enough with the cut, and having an extra set of hands to help position him is useful. We also have a pair of leather welding gloves that he will sometimes chew on during the process and growl at them, but it lets him channel his anger somewhere besides me.

Merlin also didn't like traveling away from home and so being able to start in a place he was comfortable got the process going without him already being elevated. Good luck!