Actually, for your purposes, I agree with Andy as well. If you really get into video work, then you should look into a follow focus. But for now, this solution will work for you. The strap wraps around your lens gear ring and you focus by manipulating the handle. Because the tip of the handle is further away from the lens, you have to turn it more to achieve the same focus pull but this will also stabilize your focus pulls. It also takes the focusing action out of your fingertips, which can only move the focus ring so far, and puts it into your wrists and arms like this:
[center]http://youtu.be/OAo-ZF-nXF4[/center]