Cutting a cat’s claws. Any tips?

Our seventeen year old cat no longer keeps his claws short! No tree scratching or road walking I guess.
He is fairly fit and happy, eats well loves going out in the garden, but doesn’t venture further any more.
His long claws catch on his bedding and on my clothes, leading to much shrieking and squawking (both me and the cat!).
We tried to book a cat groomer but that proved difficult. So I looked up how to do it online and it suggested using treats to reward him for allowing his paws to be handled.
That actually worked amazingly well and he has let me trim his front claws over the last week. But we’ve reached deadlock on the back paws!
Any ideas from cat lovers amongst gransnetters would be gratefully received.