Hello. We have a rescue dog now 13 years old. We have had no problem grooming her ie wash and cut untill this year. She is a German shepherd cross and long haired. All attempts to wash or cut are met with snarls and snaps. At present she is matted up and her back end is to say the least mucky. She is a happy dog, well manered, but today my wife and I tried to clean her up and she turned on me sinking her teeth in my arm. We are at a loss what to do. How can we clean her up???. Never had this problem with any dog. Any help much appreciated. Best Regards, Bernard.