I got the following question from my friend, Anonymous, in the comment section of this post about muscle memory this morning. My answer got so long, I figured I would just make it a separate blog entry.
I'm actually not that big on drills. There are a few that I use, but as you can see from the videos, I love using the tee. Hitters can work on swing mechanics and building correct muscle memory without worrying about timing or location. So we do tees at the beginning of each session, analyze videos together, and then go back to the tee to make adjustments. Those videos on my YouTube channel are mostly for the parents so that we are all on the same page. The players have already seen them plenty, so I don't upload all of them.
I also like front side short toss from behind a screen so we can put that adjusted swing to use on a moving, but easily controllable target. There is some overhand stuff, but really not that much. Once the player learns the swing, I just try to focus on one adjustment at a time, using a set of particular key words or phrases corresponding to each issue. Using tees and short-toss lets us work on specific areas over and over.
Now... finally... my thoughts on your 3 issues:
1. Hips not fully rotating: I don't work with many softball players, but my experience is that girls often don't rotate well. This is a generalization - but compared to the boys, many girls seem to struggle with getting the legs and hips involved. I sometimes do a basic hip drill you may have seen where the player holds the bat behind their back, slotted between the front/inside of their elbows and their lower back. He/she then gets real close to the tee with the ball deep in their stance, and must rotate their hips and bend the back knee a ton to hit the ball at all with the barrel. This creates a frame of reference for how much the back leg must really work in order to have a correct swing. As you know, turning the back leg/foot is the key that unlocks the hips, so I focus on that a lot. The problem with this drill is that usually the front knee must also bend in order to get low enough to hit the ball. So I use this drill in moderation. Key phrases are: turn the back foot, show your shoe laces to the pitcher, thrust the back knee in early. A wide stance makes turning the back leg (and the next issue) much easier and more likely.
2. Leaning forward: Staying back is more about key words with me - bracing the front leg helps keep the upper body back, so we talk about that a lot. I borrow an analogy from my good friend and assistant coach, Allen Sherman, who is a good hitting coach. We may have borrowed it from someone else too, I don't know: Bracing the front leg straight is like putting on the brake in a car. Unfortunately (or fortunately), most of my hitting students don't drive. But they do know what it feels like when a dog or squirrel runs across the street and their mom or dad has to slam on the brakes. There is a ton of energy created and sent up to the upper body. As a hitter, they just need to send that energy up the braced front leg into their hip rotation - not a lunge forward like in the car. So I tell them to slam on the brake and bend the back knee, and they usually stay back. They also know they want to create a straight line from their front toe up to their head. I also just talk about where I want them to hit the ball - slightly upward. Lean back and launch. If they are hitting tees, I like to stick a towel in the net in front of them a little above the ball, and tell them that's their target. Or I put a towel in the top right corner of the back of the cage for short-toss. That also keeps them back. Focusing on where you are trying to hit the ball works surprisingly well. Timing is important too - if the hitter tries to hit the ball before it gets to their front foot, they will reach, lunge, roll their wrists over - all sorts of problems occur. So I tell them to let the ball travel and get to them. Don't go to it.
3. Not fully finishing: Again, this is about key words and video analysis with me. I talk a lot about pulling the knob all the way forward and upward through contact and especially, finishing high. I want hitters to finish with their hands above the shoulders and their barrel above their head - I want them to have a high majestic finish like this guy. (This also helps with #2.) This results in fewer ground balls and more backspin line drives because it keeps the wrists from rolling over too soon. So again, no real drill. Just a lot of key phrases: pull forward, finish high.
Hope that answers your questions. Sorry to get so long-winded - I am a talker. As you know, Coach, it's all inter-connected. One flaw leads to another. But it also works the other way - set up correctly and start correctly, and things start to fall in line.