Stuns can be achieved more easily by hitting monsters' heads with Upswings or Brutal Upswings. The effect persists until you sheathe the weapon or get flinched (including roars)/tripped/knocked down.
You can perform a Power Charge to boost your attack power, stun power and flinch resistance while attacking, as well as to get access to more powerful versions of your attacks. The Hammer was built to cave in monster skulls with brutal efficiency, and it is very good at its job. This buff increases attack damage and stun damage, and gives minor hyper armor during charge attacks. Lastly, Hammers can do a self buff while charging. The moving charge attack can also be chained into follow up attacks. The type of charge attack also changes base on if the hunter is standing still or moving when the attack goes off. They have three charge levels, just like the Greatsword, but the Hammer allows hunters to run around while charging up their attack. They also have high chaining potential, and are very good at hitting the same spot over and over again, like the monster's head to rack up stun damage. The Hammer's basic attacks are surprisingly fast for such a heavy weapon, and deal quite a bit of damage. As expected, the Hammer deals only blunt damage which makes it perfect for dealing stun damage and knocking out the monster. The ultimate evolution of sticks with a rock on the end, the Hammer is a fast, hard hitting weapon.