The best dry sift ever I produced is from a Trim bin with some GSC thin mints in the cold of the mountains in December. they are equipped with a 160micron screen…
I would say the Cold and moisture are key, then is very important to NEVER touch too much the stuff you are sieving, don’t crumble, don’t even smash it gently with your hand, nothing, let it just move very delicately on the screen like when you drop some oil on your cooking pan and then rotate the pan to spread the oil around…thats the movement…slow…gentle…and thats why I didn’t like to much the tumbler because it shakes it way to much…
I tried the tumbler with dry ice and came out very green and low grade…the only advantage is that allows you to process bigger quantity but like always, quantity is against quality…then u have to clean it up
So I would say
Lowest temperatures you can get
Let the material very gently move on your screen without any pressure or smashing with your hands
Also right before sieving let the material get some moisture, not too much but a little bit to avoid vegetal dust and debris to crumble…
AAAAAAnd last but not least as usual…the genetic…usually I never got nothing exciting from sativa leaning hybrids…cristals are tooo small…best full melt I did was from GSC, OGs, Sour diesels…
Good sieving!!!