Theres no point in even dry ice sifting if your just going to throw the plant material back in after you have sifted it? if im reading that correctly.
I just made the bombest cannabutter recently , used 1lbs of dry leave and popcorn trim, dry sifted it in a 190 micron bubble bag with dry ice. Then we just proceded to make cannabutter with the dry ice kief. it came out very potent!