I recently took my first journey, and I used the GVG.
This is MY experience of it, and I'm not even sure if it's the best method, but I found it to be extremely easy, and I had an amazing experience...
I used six screens placed one on top of the one another, and then I laid down a bed of herb (CBD because I didn't want to alter my consciousness with any other substance except the DMT).
I then placed 35 mg of crystal on the bed and placed the top back on my GVG -- use any dose you feel comfortable with, obviously, but I figured if I was going, I might as well go all the way.
I used a torch lighter (nothing special, but something reliable), and I started far from the glass (I heard you don't heat the filter, you heat the "bowl" that is the filter) and made my way closer as I inhaled until I could see the smoke coming through the clear piping.
At that point, I stopped nearing the bowl, kept the flame in the same place, and I inhaled to the max (slow and steady wins the race).
Three hits (and they were NOT simple, but you can power through!), and I was gone!!
I hope this helps in any way, and I'm wishing you all the best!
"Just when the caterpillar thought her life was over, she began to fly."