I think the diet does help as well as the shampoo . Also the grooming tools . My Suzi is not great with having her hair brushed either, however this is a must no matter what type of coat.
I recently had to have her hair shaved because of the Matts. Her coat is silk on top but, cottony underneath. I have taken her in to be professional groomed just so i can learn how to handle her. Suzi is an angel for the groomer. However , a stinker for me. Offer her treats to try and calm her down and try to make the brushing as pleasant as possible. The younger they are the better it is for them to get use to daily brushing and grooming care.
I am now glad Suzi was shaved so we can start over on her hair and maintaining her coat.