Well said, Feisty. There is no once size fits all for pitching coaches. Our dd started pitching late (She was almost 12.) And started working on her mechanics with a college pitcher last fall, then dd started working with Marie Shaver this spring. We couldn't be more pleased with how things are working. Our dd is learning to build a solid base, so she can self-diagnose when things are going wrong, or right. She is learning how to think like a pitchers, thanks to Marie, and working on on the mental side of being in the circle, again, thanks to Marie.
Dave Leffew has a well deserved reputation as a pitching coach. Yet, there are some girls, and parents as well, who will not mesh with with a pitching coach, and I know of some who went to see Dave once and that was it. You've got to find a coach who clicks with your student.
Our dd's coach said that to learn a new pitch, you've to throw it thousands of time in practice to master it. That sounds about right to me. Aside from rare circumstances, pitchers are made through effort, work and committment. Constantly building on what you've learned, allows the pitcher to get better. Growing, getting stronger allows a pitcher to throw different pitches.
Sorry this is so long, but I think there is no easy way to reach success, and I view blanket statements with a somewhat jaundiced eye.