First off I am small time compared to you by far. Having 6 flower rooms about 40sqft/ea with 4 flowering in at a time and two vegging rooms with 12 at all times different satges.
For a while I was fighting PM big time. So I upped my air flow which pretty much took care of it. I still see some on the outskirts of some on outer leaves of the rooms, where the evacuating exhaust doesn't have enough pull and my fans aren't directed correctly.
I starting using this oil more aggressively, but like you mentioned it feels like unless you are spraying directly and not broadcasting all over the place its effectiveness is less.
I like my rooms with 4 plants because I can thoroughly take care of 4 before I get lazy, and start making excuses for not doing a good job. Each day a room.....one day off..snip, spray, observer and grow..repeat.
Hope that helps.
You could probably use this as a full plant dunk as well.
sounds like u got a plan that works.
air movement is key, above and below the canopy. end up shaving alot of the lower branches off an defoliate thick lower canopy areas just under the trellis. for me thats where it seemed the pm problem would return. i would not often see pm unitll harvest time. if there was a problem it was the thick leafed low airflow areas.
$17 walmart box fans are your friend for under canopy air movement. cheap, last long enough, easy to move around when working. an at that price u can buy a few an move abunch of air rather quietly.