Shaving a persian

I have 4 persians who get terribly matted. I bought a top of the line Andis shaver, and had a #15 blade put on it as a groomer suggested. Now what I want to know is, how do groomers get a cat to hold still for shaving? I got the back done on one cat after about an hour of chasing him around a small powder room, but I have no idea how I'm going to get his belly, throat and hind legs or under his front legs done. The shaver is fairly quiet, and I make sure to cool the blades down so there's not danger of burning him. I need help! Thank you.

Well, I have always beleived that they are afraid when they are at the groomers, so they dont make as much fuss. However, I think you will have better luck if someone holds while you are shaving