Cats have different coat layers. The top coat is wiry and does not matt, but it moults. The undercoat keeps them warm but it felts if rubbed. When they moult (twice a year) the coat should just slough or be groomed off. But undercoat tends to stick together and when you add friction (lying in one spot for instance, or brushing and petting) and dampness, it felts into lumps which then attract other lumps, leading to distress and discomfort for the cat. Large undercoats win prizes at shows so have been bred into modern cats.
Oliver above is persian x ragdoll, hence his lovely face. He also has a huge undercoat. His owners were aware he was uncomfortable so the offending parts were removed for him. The trouble is, the same will happen in July again, then January. I asked them to bring in his grooming equipment and first glance showed me brushes which would be excellent for a short-coated cat, but could matt a longer coat. It is harder to find long toothed combs which would be preferable and pet shops generally have little expertise in what tools are good for what cat breed. We keep a small selection and I will do another blog on grooming tools.
In the video I show the plain combs I would use and how to get to the different parts of your cat. In combing Oliver I found he has three sensitive areas, which is why he was avoiding the contact. With this knowledge and the correct tools and skills his owners have a better chance of keeping him in good shape for years to come.
Apologies for the sideways screen!!