I have the GL2 and I use it to video mine Remote Control Aerobatic Plane which can make a lot of sudden movement so I have a really hard time keeping focus.

Could you tell me some tips on how to do this...I just can't see how I could possibly manual focus all this.

Ryan,
Believe it or not, but manual focus with something as small in the frame (well, for most of the time ) as a RC airplane is the best way to go. What you need to do is to find an average focal distance of the plane to you - maybe by focussing on something on the ground at the same distance - and leaving it at that. In auto mode, the chances are that the lens will be hunting for something to focus on in all that emptyness of sky.

Robin

Indeed, once the lens is focused at infinity everything at that range will appear in-focus. That range will depend on your iris but it's safe to say that planes in the sky will generally be at such a distance.

One matter worth noting: don't confuse focus with blur. Many times new video owners (and new still photographers) will report that their camera can't focus properly when, in fact, what they're really seeing is motion blur either from the subject moving through the frame or from shaky camera handling. The closer you attempt to zoom-in on a plane the more critical your camera handling will be to getting sharp shots.

Have fun.

close the irris as much as posible. This will increase the DOF.