The spinning "tricks" have the use of making you more familiar with the staff, I think that's about it. Some spins are also components of classical Chinese forms. It does enable you to change directions, switch hands, and generally intimidate and hold at bay someone who might want to get close to you. For me, the spinning is more about learning to handle the staff, becoming so familiar with it that it moves without you needing to consciously aware of how it moves...the way you move your arm or leg.