The invisable pass and classic pass are 2 very different issues.
Invisable Pass: A successful pass is generally a result of audience positioning and a smooth execution. Speed is not as much of an issue.
Classic Pass: Speed is critical and it took me years to perfect mine. My best advise is to practice while watching TV, at work, in school, etc.
I have nevr used it as a florish until it was good enough to pass (no pun intended).
Side note: use a mirror and/or video camera.
Jeff