Freezing the stalk of the trichomes to make them brittle so that the heads fall is an illusion at best, the trichomes heads are made to fall by themselves when ripe. Would you freeze the stalk of an apple to make it fall from a tree?
Here is the science
http://www.hempreport.com/issues/17/malbody17.html
Dry sieve is more difficult to master than ice water but the result can be as amazing check my favorite Hashishin couple @cubangrower and @cubanhashqueen they make real BOMB dry sieve.
Check Boldtbags for quality bags, you want lab grade sieve material.
I understand that you are playing around and having fun but studying the basic principles of sieving would bring more fun to the game.