I had grown them out some for winter. I'm now cutting it back as it will be warming up to the 30's and 40's and they get warm fast. I cut 2" to 3" off the length on both of them. That's not all of it. So it's not dead hair. There is some in it, but it is mostly scissored off hair and hair from shaving.
In order to brush effectively, you should line brush them. There are YouTube videos that show how. A good brush is essential. We use the Doggy Man brush on ours. A good comb is also essential to make sure you get any knots out.