Gaining respect and trust with a snappy cocker spaniel

I had a neighbor called yesterday and asked if I could help them groom their 2 cocker spaniels. They had tried working on them at home and the other dog had bitten the owner on the arm. She was amazed when I put the dog on the table and started working with him. She said you could not shave the back of his head. That even the other groomer years ago did not shave the top of the head. All it took was rubbing the back of the clipper instead of the blade around on the head so that it would learn that it is not gonna hurt him. I had recorded part of the grooming. She ask if I could send her husband part of the video because he didn’t believe that I groomed them so easily. All it took was working with him for a few minutes to gain his respect and trust.