And now---THE SECRET.
I learned it many, many moons ago, when I used to go to the original Yankee Stadium every chance I got. I would sit in the upper deck behind the plate, where I could get a nice panoramic view of the whole playing field, and I would watch the pitchers, particularly the Big Three---Reynolds, Raschi and Lopat. And I saw what they were doing---and how they were doing it.
They were all driving off the lower half of the body, using the legs, the hips and the torso in one continuous (and, it seemed to me, seamless) motion, creating a nonstop flow of energy all the way up through the shoulder and the arm to the fingertips: as if the ball itself were an extension of the arm. They were generating power behind their pitches, even Lopat who was not a fireballer, and throwing harder with less effort, which took a lot of pressure off said shoulder and arm.
I saw what they were doing, and how they were doing it, and I made some careful notes so I could start working on this essential element of good mechanics. As I practiced this I discovered that I was doing the same thing those three pitchers were doing, and because I was a natural honest-to-gosh sidearmer my delivery acquired more snap and sizzle---including the crossfire which I had just picked up.
I don't know what they called it at that time, but nowadays there's the "Hershiser" drill, which aims at getting the hips fully involved in the process of throwing the ball, and you would do well to look it up (I think you can find it on YouTube) and get to work on it. There's no special equipment involved, just a fence or a wall. That will do for a start, and later on you can work on picking up more arm speed and the like. The whole idea is to get the entire body involved!