question on bar mobility drills

Are we supposed to move the bar using only strength? when I try to get the bar over my head my hands start pulling away from each other and I have to grip really tightly to hold on. I feel like this makes it easier. Should I try and avoid having to pull? Heres a video of what I can currently do. This thing ways like nothing but its hard to find a bar under 15 pounds at the gym. I notice that it is way harder with weight though. http://www.youtube.com/watch?v=yviiQmfg6_c&feature=youtu.be