Please, please, oh please do not ever, ever use a pair of scissors on a matted cat. You will be coming into my office with a laceration that needs stitches before you can say, "unhappy cat". Instead, I beg you, accept two small bits of advice: Brush your long haired cat to prevent matts, and buy a pair of Oster pet clippers in case you ever feel the need to cut a matt off at home. Yes, there will be times when Mittens gets a matt in that lovely, fluffy coat despite your best preventative efforts. Yes, there will be a time when Junior brings home a matted, stray, flea bitten cat even though you've told him not to touch strange animals a million times. If you follow my second tidbit of advice, you will be prepared for both events. A clipper is infinitely more safe to use to remove matts than a pair of scissors.
Small, loosely adherent matts can be removed from a patient cat by gentle pulling. Hold the matt in your stronger hand, and slide two fingers of your weaker hand across the base of it. Draw the matt away from the body with the stronger hand while pressing the cats body and rubbing with the weaker hand. This putts the pulling tension on the rot of the matt instead of on the cat's body. I prefer this to use of a comb because it's swifter and grabs smaller amounts of hair. Larger matts and matts that hug the body can't be addressed with a comb, either. Clippers are in order here. Combs and brushes are for preventing matts, not for curing them.
The proper use of a clipper can be demonstrated by a groomer or a veterinarian. If you have a groomer or a vet who doesn't have the time to show you how to use the clipper, shop around for another professional. This is your chance to see see how that person responds to a request for a little extra attention. If she can't show you how to remove a matt now, chances are good she won't have the patience to answer your questions about a serious health matter later on in your pet's life, either.
Finally, if your cat is not compliant, give him a break! You don't want to get bitten or scratched. A healthy coat is important to your cat, but healthy skin is important to you, too. Cat bites really are a hazard, especially to older people and anyone with immune compromise. Some cats need to be sedated for grooming; this is okay! It doesn't mean you have a bad cat or that you're a bad owner. Think about your willingness to accept whatever the dentist can give you for anxiety and pain, and be glad that you and your vet can offer the same relief to your anxious cat when in need of heavy duty grooming.