The other thing to understand is each difficulty level has different optimal times to time the release for a ideal, early or late delivery. Do the practice mode with the difficulty level of choice with the bowling meters on and with the tutorial mode turned on. This will slow the game right down at the point of optimal for both the jump and bowl action and let you see where your player is at the time to be able to judge when the optimal time to move the control sticks is.
Alternatively, disable the tutorial mode and just video record yourself with a phone or something going through the motions with the bowling indicators turned on to see the part of the animation the bowler is at when the dials reach the optimum points.
Secondly, helps if you're on a good pitch that promotes bounce, and obviously, with a nice tall fast bowler. I have been struggling getting anything more than a few inches over the bails even with a short ball and early pitched delivery with my fresh career pace man.. but when I tried Mitchel Johnson in a casual match on a hard pitch, first bouncer smacked the batsman fair in the grill.. second was a full pitched swining screamer that thumped into the pad for a plumb LBW decision.. just your typical Mitch work (made me whoop in delight I must say).