OK, here's what works for me.

-I open the air flow wide open.
-I pulse it first to make sure the battery is strong and the wires turning red hot in ~1-2 seconds. I think that preheats the crystals so it heats up faster when you want it to.
-I weigh and load my standard breakthrough dose from my GVG. I poor it right in the center making sure it's not stuck to the sides, so I may push it with that little spoon that comes with it.
-Then I melt the spice, watching it closely, by barely tapping the button until the powder is gone, but not enough to make any smoke, and I make sure there isn't any spice left sitting atop that center square.
-I exhale all my air, before I start.
-I hold it vertical so any DMT doesn't run to one side, but I don't think about that too much.
-I hit the button and hold it down and within a second or so I'm inhaling off of it as hard as I can.
-Perhaps 5-7 seconds later I get a sense of heat going down my throat all at once but it's not that bad, but it feels like it's all vaporizing at once. I feel like that's the moment you swallow the alien, but I keep inhaling until I'm sure it's more than 10 seconds.
-Then I usually inhale a little fresh air on top of that so my lungs aren't still half empty and hold my mouth shut with my hand just to make sure I don't cough, and hold my breath for 15 seconds.
-Lay back and enjoy the ride!

It's harder to explain than to do.

The one thing I like about the GVG more is the unrestricted air flow, so the Yocan feels a little claustrophobic at first and the vapor maybe more dense and all at once but sucking a little air on top helps a lot.