Then I watched the in-game gameplay demos that teach you how to play... there are 20 of them in total.. the first few just show kirby on linear straight courses to demo the ground/fly shots... then there's a demo with a dpad picture that is a full diamond-shaped course that shows how to aim your shots.
I really like how L and R are used to quickly adjust angle by an exact 45 degrees.
It seems like going for the middle of the power meter is what you need to land a straight unobstructed ground shot at exactly where the end of the guide is... but for fly shots you have to stop the first meter in the middle, and the 2nd meter at the top to land exactly where the guide shows... (er, actually it looks like you actually want both meters to land in wherever the white line happens to be... I just got confused by the redundant bar meter on the right, when you actually need to look at the crosshair meter where Kirby expands/deflates across both axis)
Ground curving seems pretty simple too... just the same as aiming except you have to hold B... the guide shows the exact curve you'll make if you stop the meter in the middle.