When Jaime speaks of the "going to the bathroom" push sensation, it's not the vein popping, red faced, constipated push, it's the isolated in the lower portion of the body push - but then only the stomach/lower ab muscles, leave the rectal muscles tight and out of the push... or singing will be a messy business LMAO.

Okay, gonna get blunt here for a sec.. cause.. that's what needs to happen to explain it right.... THAT SAID... when you push out a fart, or squeeze too much for a #2 you hold/lock the lungs, that is the part you DON'T want to do because it's actually your chords that are holding back that air, instead use that TYPE of push minus the lung lock to slowly and STEADILY release the air with a relaxed chest. You are now actually controlling the airflow WITH your abdominal exhalation muscles instead of trying to hold back a flood with toilet paper

Pretend you have "dead lungs" and all of the muscles associated with "top breathing" are dead too, just use your abs. Once you've got that sensation down then work in the muscles that expand your ribs apart from the outsides. like you're puffng out for dominance or a fight on the inhale - WIDE though, not chest up/out.

Now you're a giant sack of air, like a bagpipe your sustain and power will change based on how much air volume you allow with your abdomen. Again, can't stress enough, all the support, the air pressure is done by "bearing down" with the abdomen or not.

NOW that's the breathing portion, the other 3/4 of the support is the balancing of vocal fold tension (with minimal stress), resonance placement and the shape of the mouth and palate.