How to make grooming bearable for your dog
If the dog backs away from the brush or tenses when a paw is touched, start with an easier task. Forcing the whole procedure to the end is not a good measure of progress. For a sudden change or suspected pain, get a veterinary assessment first.
Pick one procedure and separate the first step from the procedure itself. For brushing, that can be the brush simply being present, calmly. For a paw, it can be a brief touch that is already tolerated. Finish before a struggle becomes necessary. The next level of difficulty is chosen by the dog's reaction, not by a promise of results in seven days.
Use a suitable reward and a calm setting. If the diet has restrictions, agree the rewards accordingly. Allow pauses. A note like "allowed one calm touch and moved away" is useful; the word "stubborn" does not tell you what to change.

The AVSAB professional guidelines support reward-based training and reject the use of pain and fear. When you seek help, ask the professional how the task is adapted and what happens when the dog refuses. Do not settle for the label "positive" alone.
For strong fear, a risk of biting or a procedure that cannot wait, work with a veterinary team. Sometimes the goal is safe professional handling with a plan for the next visits. Home practice must not delay necessary care.
Use worksheet 5 in the handbook (PDF in Bulgarian) to record the small steps. There is no required length for a session and no need to buy a new tool before you understand what the dog finds difficult. The fuller approach is in chapter 2 of the handbook; the short brushing steps are in Guides.
General care information, not veterinary advice.