AsNoriuanswered grow question 3 years ago I am a big fan of defoliation , but you have to have right plants for them what to takedown, good feed - for them not to struggle, good humidity - for best VPD, good light height, for having them high if they grow...
In veg I do it few weeks before flip to flower, like week 5 or so, then before flipping, 2-4 days I train them last time in veg.
In flower window is open from 14, till 20 day of flower, very dependable how quickly bud sites are formed, you see small flowers everywhere - good time ! Still only top forming - too early.
Next wave I do on days 40-45 of flower, when bud is almost formed and just pumping to fat ass left.
Try not to touch pistils, do it before watering, don't feed in that watering and they will recover in less than 30 hours.
Leave top nod fully formed matured fan leaf set, anything below - you can trim. I do lolipop sessions together.
Look at my Seedsman third week of flower and recent update, even having problems with overblast of light it's jungles again !
Good luck !