Since the Bullmastiff’s short-coat tend to be naturally water-resistant, it’s advisable to avoid water-cleaning him regularly. Instead, use a specialized dog shampoo to bath him when absolutely, such as when really dirty/smelly. The long duration between whole body baths allows his skin to remain well-oiled and balanced. If you want, you can clean the legs, face, and even the stomach areas frequently. This, together with a good combination of dry shampoo washes should be enough in between the months. Leave the thorough water baths for twice or once a year