Calming a dog who dislikes being groomed can be a gradual process that requires lots of patience and positive reinforcement. Some things you can do include: gently desensitizing your dog to grooming tools and activities, offering treats/praise/affection during the entire process of grooming, beginning with short grooming sessions and gradually increasing the duration, and providing distractions (like toys). If your dog's aversion to grooming is severe, consider seeking help from a professional dog trainer or a veterinary behaviorist.