I found that six-axis-guiding anything in this game was impossible. I immediately went into the settings area of the controls and cut off the six-axis motion controls. It worked a lot better for me once I was aiming normally again, with toggle sticks.

You may want to suck it up, and turn "Six-Axis" off just for this game, so that you can really enjoy it. I found the motion controls to be too distracting and hard to use. By all means though, try what shootemhigh says first... I'll admit that he seems to have had a better grip on the situation of slightly moving the controller. I probably went into it too crazily, and that may have been my problem.