My grandma-in-law recently passed away and her 13 year cat came to live with us today. Of course he is going to need time to become calm around me and I don't want to put any added stress on him, but I noticed he has mats in his very long fur. I know these can become painful so I don't want to leave them very long. How long should I wait to start getting rid of the mats? I was planning on doing one at a time with plenty of rest before starting on another one. Any advice would be greatly appreciated. Thanks!