Dave Re wrote an article about the ball & dummy drill. He challenges the notion that it’s a good drill for curing flinch, offering his critique as well as a better drill.
Give it a read. It’s good food for thought.
I still think ball & dummy is useful because, if nothing else, it helps to make a shooter aware of what they are doing. Most of us will never SEE ourselves yanking the trigger and be aware that we’re doing it, until we press the trigger, there’s no bang but there’s one hell of a dipping of the front sight. So if nothing else, to that end, it’s a useful drill towards helping identify and become aware of a problem, which is really the first stage of fixing the problem.
But no question his suggestion of a solution is useful. I think Karl called it “zen shooting” to me. It’s slightly different but the point remains the same: shooting into the berm with no specific target so that all you do is focus on the front sight and watch the front sight as it moves. You learn a lot.
Stuff From Hsoi 
Wow. Good reading. When I was younger I would see my friends shooting great groups and then if they had a malf or ran empty and didn’t realize it they’d appear to “jerk” the trigger. At that point I realized that their “jerk” wasn’t the same as a novice’s jerk. I like the terms “pre-ignition flinch” vs. “post-ignition timing”.
At the last class I took with Karl I thought the ball & dummy drills were more valuable for malfunction-clearance drills than anything else.
I’ll have to try the “zen shooting”. Can’t say that I’ve ever unloaded into a berm while observing how the front sight moves. I guess I’ve always focused on realigning the sights and not what the sights are doing when I’m not pressing the trigger.
Ball & Dummy is good for making you aware of the problem and trying to get you to stop doing it. I think Karl wrote somewhere that a variant of the drill is to KNOW where the dummy is (e.g. load your magazine known alternating real round, dummy round). Thus when you know it’s coming, you tend to make every trigger press a good one.
And the “zen shooting” is a useful thing too. Just stand close to the berm (ensure visually clear background, and that all rounds will go into the berm), don’t observe the target — as we typically do because we put a target down there. Instead, just keep your eye fully focused on the front sight and watch it. Do this a lot. Watch and observe. You learn a lot.