Ohhh goodness my hair sure does get matted post braids. And it took a lot of crying and research to figure out how to detangle matted hair. Please don't do what I did, and try to fight your hair with the comb post braids. That was the worst thing I had ever did. It didn't work and my hair looked like a giant mess. There are a couple of ways to get your hair detangled.
For this method you either want your hair a bit damp, or completely dry. Ideally you'll want to use deep conditioner. You'll want the conditioner to soak into your hair for about 30 minutes. After that, you can work slowly though the matted hair with a comb.
Apply the treatment to the matted hair and rub each section of the hair separately.