clean hands, latex gloves, an alcohol cleaned scalpel and steel tweezers, I crush the little(1/16x1/16ish) bit right on the window with the scalpel, one push I see juice and remove the cabbage leaving the juice.
I love growing high brix cannabis but smoking high brix cannabis....not so much. theres a really cool window of opportunity you'll find for your perfect harvest moment. Get a chart for awhile, pick a keeper plant you already know and stick with testing just that one, unless you're industrious with oodles of time, do them all then.
check brix lights on lights off, mid lights, (sry) I dont know your grow techs but check minutes after a flood/feed, hours too, next day.
pretty soon you'll see this pattern evolve.Try to stick with exactly what you already know for now, dont try to change brix (well, industrious, etc)
when you see this pattern I dialed down (settled down) my brix checking but also changed the way and times I feed and water for instance. I changed up my c02 cycle also, found I didnt need so much to ensure thriving metabolism so I cut that down a bit. harvest times are optimized as they are with the fruit of my orchards. I've tested those tree leaves too but they're always awesome so I stick to the fruit when I think its close. I've pushed my apples to 18 but I really think the sweet spot for them is around 16. Store apples have been 7, 11 ish, yuck, my neighbor likes 12's, so......its up to you. and consider this has little to do with cannabis buds, as thats not fruit like apples. and you arent eating them, if you were a high brix would be sweeter, but high brix at harvest is unburned carbs and will take fermenting to rid your bud of the icky.( overfed organic>overfed bottles imo)
your brix reading will show you things like metabolism, general health, root health, uptake over/under feeding maybe more.
brix readings are sluggish under (older?) inferior lights compared to hid's for instance.
if mine (3) broke I'd replace them all, one in the garden shed, one in the drying room/house and one in the mj garden