FWIW, here's my explanation. When shooting my 40 cal as a newbie, I felt like when I dropped the tonque (sorta like spitting) I only needed to release air built up in my throat because of the small calibre. With the big bore, I visualize emptying a complete buildup- throat AND lungs. So after this initial explosion, I feel an extended release, emptying the lungs as well.
I don't have anything, but i use the old school Cherokee method of supporting my upper arms on the sides of my chest, puffing out my cheeks and 'valving' with my tongue. There is a sweet spot between not enough power and overdriving the dart. I always make sure my nose (and therefore my eyes) are the exact same distance above the gun, usually one finger width. I try to remain absolutely still, and let the dart do its work. I of course look only at the target, and put the spirit path between the two blowguns i see in my unfocused vision on the target for windage. If you look only at the target, you will see two blowguns. The one you feel in your hands and its spirit brother beside it. The long space between them is the spirit path. Rotate your head slightly from side to side until the spirit path is level. Let it lead directly to the target. All you have to do then is allow for elevation by raising or lowering the gun. That is a matter of practice. Anyway, that is the way my mother taught me over fifty years ago. Still seems to work. You need to be able to hit a quarter from twenty five or thirty feet to gig frogs, and this method will deliver at least that accuracy.
Oh, and think short fierce puff, not long breath. It is like saying the word 'two', and immediately cutting the air off. Always EXACTLY the same, no matter what gun you are shooting. Your breath is your "gunpowder". Measure it carefully for each shot.