It is obvious on these forums who knows what they are talking about to the others who have some idea about what is going on. For example, I know Nellie (and I don’t know him or her) can hit it because anyone who is competent with the shot knows it isn’t nearly as hard as many believe. I actually hit one every couple of weeks, sometimes weekly. As Nellie says, it really isn’t that hard of a shot IMHO.
Yes, the timing is crucial as is putting yourself in the proper position to hit it but beyond that, it isn’t too bad. It does require precise timing and it is much easier when running back full speed as opposed to having to slow down into the ball but any reasonably coordinated person can learn it without too much difficulty. The hardest scenario is a high shot that doesn’t penetrate the court and falls almost straight down as the timing is very precise. Of course in a real match (i.e. not screwing around) you wouldn’t be hitting this shot because you could get behind it or even hit an overhead maybe. It just looks hard. It is not dangerous unless you are uncoordinated and I have only ever nicked my leg once in 20 years of hitting this shot (after a long layoff).
The people who miss it and don’t understand why (and look bad doing it, which is easily fixed) who think the legs are in the way are just trying to hit the ball too far in front of them (toward the back fence) and running into leg problems. If you are hitting it in the right place, the legs are not in the way. Here is the short version of how to hit it. It is much easier to teach in person than just writing about it.
First, your contact point is actually right under your coccyx give or take a few inches (probably slightly closer to the net when you are running toward the fence). You can’t hit it in front of your legs or you won’t pull it off. Your contact point is 4-8 inches off the ground just before it hits the ground on the second bounce. Here is where your timing comes into play. Using a continental grip, you just snap your wrist through impact and extend between your legs. No need to contort or lift your legs at all. If you are doing this, you are trying to hit it too far forward (toward the back fence). The right contact point makes it much easier to hit consistently.
Here is a progression to teach yourself to hit it. Step 1: start facing the back fence (at about the service line) and drop a ball with your legs spread a bit and just hit it and extend between your legs. You are just finding the proper contact point and learning the timing of the shot. You aren’t moving so you can work on just hitting it in the right place. After you master this (i.e. can drop it and you can hit it over the net behind you essentially every time you are ready for step two. This is all you are doing except instead of stationary hitting you are hitting it and moving which is why the timing is so important. Step 2: begin facing the net and lob the ball over your head (just enough to carry your head). Turn around take a few steps as needed and hit it between your legs like you did in step one. This is the hardest step probably as now your timing and proper spacing on different balls over your head will take some time to get the hang of. After this gets easier for you, then start feeding yourself harder balls; some higher, some lower, some where you need to move quickly back to the ball and so on. When comfortable with this, move to step three. Step 3: have a buddy feed balls over your head when standing in a volley ready position a few feet from the net. This simulates a worst case scenario as you have to cover more ground than you usually do when in a more normal volley position.
Just practice this and in some time, it will become second nature. You can teach yourself this pretty quickly, especially if you have someone there to demonstrate and break it down what you are doing wrong. I only hit this shot when I have no other choice in a match because at the higher levels, you will rarely win the point on it (or am goofing around or to teach someone how to hit it). But it is surprisingly effective all the time at 4.0 and below (because most are so surprised to see it hit or have never seen it in person that they fluff the volley).
Best of luck and see you on the courts.
TM