Your Tosa Inu has plenty of strength, even as a young pup, but if you don’t train him to be calm at a young age, fighting him when he is full grown can be overwhelming. To tire your pooch out, take him for a nice long age-appropriate walk. Let him sniff, pee, poop, and get all of his wiggles out.
Create a grooming room, one that you will use each time you groom him. Add a radio or a place to plug your cell phone in and find some nice calming music to play while you are grooming him.
Make the room smell so good by putting a small amount of lavender essential oil in a diffuser and giving it a few minutes so that the scent has fully filled the room.
When you go to the barbershop or salon, your stylist talks to you the whole time they are working on your hair. You can do the same thing for your pup; a calm soothing voice will help further calm him down.
There is no reason to be in a hurry working on training him to be calm, let him set the pace as this will make the whole process go far more smoothly.