Leaves are fanning upwards and undergrowth is huge...

When mine get to this point, I deleaf anything that doesn't have trichomes showing or are laying ontop of another bud..the flower auxins are in abundance and allowing a higher par down deeper into the canopy can really help out lower bud development. One rule I follow is to avoid removing more than 30% of the canopy on any day, usually followed up with a light nute application and a few days rest before another selective deleaf. To this end, I've reduced workload during trimming and have had less popcorn buds. On a side note, resin production is a defence mechanism of the plant to discourage browsing by pests. When the right amount of leaves are removed, the plant will respond with an increase in resin to counteract the browsing.. I don't know of any science study's that have been done in this area, but my trials have shown a noticable difference.. Cheers