
Hi
I always used at least 2 different brushes/grooming tools on our gsd when she was with us.firstly a slicker brush was a must to get all that undercoat out. a detangling comb, and a blade, i think it is called a shedding blade

I can't remember off the top of my head, but all these can be brought from PAH. the coat is probably the top coat that is coming off on you, but the shedding blade will help to reduce this.