If they're stubborn you may need to repeat the fill/empty cycle 2 or 3 times. 100% success rate for me and my family and friends. I guess the it helps relax the diaphram to take control of it and put it through its paces.
1. Inhale until lungs are at full capacity.
2. Hold your breath as long as you manage comfortably.
3. Breathe in and out slowly for a couple of breaths. I.e. don't gasp for air.
I also long suspected it may work by reducing the activity/stimulation of the diaphragm.
I think my version works because the diaphragm can’t spasm when it’s stretched (or contracted, not sure which) so far out from its neutral position. If I think of it next time, I’ll have to try your method out!
Never tried it, but it is firmly planted in my head as random trivia.
[1] https://malct32.blogspot.com/2011/03/rectal-stimulation-to-c...