The basic gesture is very easy to learn and use as the following:
Extend your Thumb and Index finger straight. While hold the position of your two fingers, use your Index finger slide on the side of your phone to guide your Thumb finger drive the ball straight towards the pokemon.
HU Style insures your Thumb finger moving straight regardless how shaky the environment is.
Once you mastered the basics. You can add movements to your Thumb finger to throw curved ball for example. The key invention is to "use your Index Finger sliding against a side of the phone".
As the inventor, I named the gesture as "HU Style". The name helps you to remember that your Thumb finger and Index finger form a letter like "h" (left hand) or "U" shape when you drive balls.