Sitting here at the computer, I can visualize this technique quite readily and "practice" to some extent.
As I near the end of my exhale, my breath is moving more slowly and I start my gentle squeeze on the trigger and by then, I should be mostly sighted.
I allow my exhale to complete naturally, on its own without consciously pushing any air. When the exhale is complete, I pause before inhaling and during that pause, I can make a final adjustment to put the crosshairs on target and finish my squeeze. I don't know when the shot will fire so I do have to hold my breath for a moment or two. Not longer than three or four seconds, though I'm not counting.
At the beginning of my exhale is when I relax completely. The whole exhale can be described as allow the air to kind of "fall" out of me or find it's own way out without any help from me.
But that's just me!
--Wag--