Brushing out mats requires time, patience, and involves some pulling. If the cats are only just getting used to being groomed by you, then you could lose some ground working them out yourself.

If you can cut them out, that will be faster.

Or locate a groomer. In most states, a dog groomer is NOT licensed to work on cats; they are two different licenses. But a few phone calls will help you find someone.

I didn't notice which state you are in. I took Vita in to PetsMart in Salem NH last summer when she got mats on her belly for the first time ever; she is 9 years old. I didn't need the wash, dry, fluff routine, just shave out the mats. I explained exactly what I wanted. It took two people, one to hold her and one to run the clippers along her belly area. We were in and out of the store in 15 minutes; I think it took longer to check out at the cashier's at the front of the store! And the best part? It wasn't me she was mad at, he he.