Having owned my own custom auto Upholstery business, I can tell you it takes a lot of practice and experience to become good at it. But, just like everything else, it really isn’t that hard to do once you learn how.
The main reason I retired from doing it was the carpal tunnel syndrome that was developing. I used to spend every night soaking my hands and wrists in very hot water followed by long soaks in ice water just to be able to make a fist again.