How do I make the static poses of the characters?

What I want to do is that when I press the shift key the character should cover himself with his hands so he doesn’t take damage, but at the same time he should be able to walk (move backwards or to the side). I’ve done this animation tutorial but I still have no idea how to achieve that.

What I want is for the hands to remain static but still the feet to be able to move if the player so desires.

How are those static poses done and how can I mix them with other animations?

Set the Animation Priority to Action, and only animate the arms and hands. Any body parts that aren’t animated will be able to move with other animations.

then the whole animation should be a pose? How long should that animation be? And if the other animations have a much longer time, could that affect anything?