I was taught...
Breathe deliberately. When it's time to squeeze, stop breathing deliberately.
In other words, don't wait till the end of a breath cycle. Interrupt the cycle you're currently in with a stop, squeeze, start breathing again. Interestingly enough, START breathing again after a critical shot is something a lot of people don't do well.
That's old school, too much to think about, where as you naturally stop breathing at the end of the breathing cycle.
When I was really heavy into High Power, while coaching the AK NG Rifle team, I shot rapid fire fairly fast, We had 60 seconds to get into position, fire two rounds, reload and fire 8 (200 yard setting). I'd shoot it in about 45 seconds. Even then I'd check the spotting scope after the first to rounds to see if I needed an adjustment, sometimes I did and would make the sight change.
I was at the Wilson Matches (National Guard Championship) and after firing a string the guy scoring for me asked how I breathed while shooting so fast.
I didn't know. So the next string I tried to think about my breathing so I could relate how I breathed. Worse Setting Rapid Fire string I ever shot.
The next day he ask his coach to watch me regarding my breathing. His state coach said I breathed in, out, fired, breathed in, out and fired. I had no idea, it just came natural. If I tried to think about it, I'd screw up.
The more natural an act is, the more constant you'll be, the less you think about something, the less chance you have of screwing up.