I trim all my cats claws regularly. Mazy was the only one who needed several years of Paw Work to accept it and I don't do her hind feet, only front, Tolly and Jennie get hind and front done.
Mazy cat's Paw Work was: daily I would hold her and touch her paws, giving her little dots of mayonnaise as treats while I did it. It took time for her to even allow me to touch them long enough to press them and extend the claws. It took over three years to actually get to the point where she would allow me to clip them. At first I could only clip one claw at a time, then gradually she would accept a whole paw at a time (continuing with the mayo treats, she can't bite if she's licking mayonnaise off her mouth) and now I can do both front paws in one session.
I advise you to start getting Cappy used to having his paws handled in the way I did with Mazy. Hold the paw between your thumb and fingers and gently press to extend the claws.
This not only gets him used to it, but gives you a chance to observe his claws. Observe how they grow and where the quick is (the pink part)
When starting, just snip the tips until you develop more confidence and skill. Eventually you should be able to cut them a bit shorter, always avoiding the quick-which is the pink part.
I use these clippers, and replace them yearly, as they do get dull with use.:

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