the best tool for combing out a knot is a shedding comb. This is a comb with alternating long and short teeth. It is fantastic! I could not do my job (pet groomer) without it. But knots DO pull at the skin, so they are uncomfortable for kitty. That is at least part of the reason she fights the procedure. I would NEVER use a scissor on a cat. too risky. if a mat will not brush out, a clipper with a short blade (#10) will do the trick a whole lot safer. Keep in mind that when a mat forms it pulls the skin (to prove this hold on to some hair and twist it and watch the skin pull up off the body). That is why the scissors are so dangerous, the skin gets folds that you would not expect to be there. work with the comb and a slicker brush doing very small sections at a time, and when in doubt call a professional.