I moved the compressor very close to breaker and ran a short hose to the
pressure port. This allowed me to blow out my sprinklers properly. The
breaker stops "gurgling" after I give it enough airflow to "open it", at
which point the air goes to the heads and they pop up. That point seems to
be an indicated 65-70 PSI on my compressor output gauge. Once the heads
pop I can immediately reduce the air pressure and the breaker will remain
open with the heads remaining up. I reduced it to an indicated 50 PSI
after the heads popped up. The heads will remain up even if I dial the
pressure down to an indicated 25 PSI.

My compressor was not able to keep up with the airflow at 50 PSI so the
pressure dropped slowly as I blew out the lines. I had to cut the airflow
to allow the compressor to catch up a handful of times.