I have not ever used dummy rounds. I should maybe.
But I use dry fire between firing live rounds.
With rifle I shoot 223 so flinching really is not why I do this, mainly to improve trigger pull.
With 9mm I have trained people who never shot firearms before to keep inside paper at 10m by changing between live and dry firings. Friend of mine still continues it today himself. But it really works well too.
With rifle:
When you do the dry fire, focus on
1. Relaxed shoulder, but firing hand is still supported
2. At this time, check NPOA. I have sometimes noticed it changes after previous step.
3. Trigger pull, I start counting steadily 1-2-3 while I pull and on three it should break. I do not force the last bit if it does not break, I redo. But I use stock trigger which is horrible compared to competition stuff, like my B&A. Hence the reason I practice it.
Do the dry fire until you are happy with the result. Then return to live fire for 2-5 rounds for intense training. I bet you will see improvement, as you catch yourself doing stuff you practically should not. As you get conscious about the matter you can begin to change it.