I've used my gvg a total of 5times. It works well, but it's tricky to use for me.

I stopped using it when i started making changa. It works extremely well in a regular bong with a regular lighter with very minimal combustion.

What i do is just hover the flame a few cm over the changa & slowly start taking a hit, DO NOT cherry the whole bowl. Just gently knick a very tiny edge of the changa with the flame & continue hovering the flame above the changa.

The bong will fill with what looks like very thin smoke, this is just a mix of a small amount of smoke & dense vapor. There should be very little taste from the minimal combustion.

You'll know your getting vapor & not just thin smoke because it has a dense feel in the lungs & tends to cause a little bit of a tickle when held as if you need to cough. It shoudln't be rough.

Viola, no headache.