My routine is similar, except that my step 3 is a further “sipping” inhale, repeating your step 2 and my step 3 until I can’t take in any more air or hold my breath any longer. I’ve found that the initial “max capacity inhale” really isn’t that, but it takes some seconds holding that much air in at rest, with the trachea closed, in order to further inhale.

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!