With my very first cocker I had the same experience. I took him to a groomer and he came back looking a little worse for wear. They told me he bit the groomer. Then and there I decided to learn to groom for his sake, just like Manuel said. Back then it was harder, I relied on myself, and my internet friends to explain what to do. Over the years there are many grooming DVDs and even uTube videos available to explain the process. There is nothing wrong with using a muzzle, I have one here that sometimes I have to use. My youngest baby (he will be 4 on the 21st) has never liked his face groomed, he would stand it for Robin, his groomer, but, not for me. So, I have my husband hold him, and hold his front paws, and zip zoom he's done. I like doing my dogs myself, it's so much cheaper, and, I like to keep my boys groomed pretty tight. So, it works well for me. Pratice makes perfect, and, your dog doesn't care if he's a little rough.
Another suggestion is that if there are dog shows in your area, find one that has a cocker club and attend the show. Go back where the dogs are groomed, get friendly, ask questions, etc. Show breeders, if they are not behind schedule, are usually always willing to talk.