Coal sifting screens. 105 micron screen on top, 70 micron below that one. I usually use popcorn buds when I sift. I find that leaf trim makes great hash but more particles finds their way into the final product and you don't get that melty goodness. I'll use leaf trim with dry ice.
For making full melt, I make sure my popcorn buds are super dry... to the point where they break apart with a little pressure. Since Most of my hash comes from my outdoor grows, I have Lots of time to dry and cure it before the cold weather hits. I wait till temps dip down to -15 or so and the humidity drops off. My screens are metal so this also helps to keep the temps low and not transfer any heat to the plant material.I find that the colder it is the easier the Trichs are to work with. The most important part to making full melt is to not apply pressure to the plant material.... it forces small pieces of green material thru the screens and taints the heads. It can be cleaned out by running it thru multiple screens but it's alot of work. If you don't fuck it up from the start... there's no need to have to clean it after.
So I start by separating the small buds from the stocks and collecting them on my screens. I then begin breaking them to pieces that you would consider too small to roll a joint but not to the point of dust. No pressure on plant material on the screens. I don't rub, I don't card. I literally let the material land on the screen and let it sit for 15 or 20 seconds before I scoop it up. I know this sounds ridiculous, but I'm not worried about quantity, I'm going for quality. This material can be run a second time for a slightly lower quality but still awesome hash or if you are like me, it's time to make some butter and make some edibles.
I find the material that falls thru the 105 but stays on top of the 70u is the money. Most of the stuff that is below the 70 is broken stalks or plant material and can be added to your edible pile.
The return is low on this, for every 100 grams of popcorn I usually get about 5 grams of really really good full melt. I can usully get another 7-10 grams of decent hash but it's not the terp heavy, sticky, melty stuff.
Basically its quality in equals quality out. You can only get good results if you start with good material. My old man always told me that you can grow good weed shitty, but you can't grow shitty weed good. Same goes for making hash.
Makes sure the temps are low, the herb is dry and cold and don't use any pressure. It's simple... but it took me along time to get to the point where my dry sift bubbled. It used to drive me nuts that I couldn't do it. But when I learned the no pressure and no carding trick, it was a game changer for me.