Perfect answer. It needs to be second nature then you brain forgets the stupidity.My DD would do it every time she laced up her cleats. It was part of her warmup for practices and games. Contributed significantly to her velocity.
I'm not familiar with J bands but here goes. The angle constantly changes, so there's nothing certain there.. 625 if you want to share what done properly means? I've seen the videos from J bands on long toss but that's about it.
You need to throw the ball like you're throwing to mom or dad in the backyard. Smooth and over the top. Just laying it in there. If it bounces in front of the other player who cares. The object is to keep p that ball on line as simply as possible. Take a few throws then a step or to back. You have to find the point where fatigue starts to build.
Once she's comfortable and her endurance builds have her do a pull down from her longest point. Pull down is just a rocket. Again all you care about is the ball being on line. Skipping or 10 bounces means nothing in pull down
Do it regularly and often again it's about endurance