Okay, after a TON of obstacles and hassles, I finally got to use the vapo-bowl. The set-up is an upright water pipe with water, whose original down-stem was replaced by a 14mm GONG diffuser (fastened on with rubber gasket), into which goes the 14mm vapo-bowl (with steel screen). The herb is medical-grade quality, and fairly dry, but not-bone dry (dry enough to snap the stem when bent, but not enough to crumble by rubbing in between fingers). Herb was broken up as finely as possible by pulling apart with fingers. Results as follows:
My first impression was that this thing is incredibly difficult to use. I had the herb in the "lower" position (under the pinches) in the center of the screen. I'm using a Colibri jet-torch lighter, and initially I was playing it safe and careful. First few tries I had the jet flame perpendicular (horizontally across the VB spout), and allowed it to barely dip into the spout with long inhalations (20-30 seconds). After so many tries with this method, I wasn't getting anything like a milky-rope of vapor that is possible with the VB, and we are talking a TINY amount of herb (like .05g, even less).
Then I tried 45 degree angle for the flame (halfway between horizontal and straight down into the spout), allowing the tip of the flame to dip in. I could taste some slight vapor, but still no "milk".
Finally I figure I need to step it up and use a 90 degree angle (flame pointing straight down into the spout). Few tries and I get a very slight amount of visible vapor. I am frustrated, I've been at this for 2 hours straight (because of lighter refills). The herb is bone-dry now, but shows no signs of being "browned". At this point I am actually TRYING to combust, just to see if it's possible.
Now it's balls to the wall. This time, with the flame pointing straight down into the spout, I actually allow the ENTIRE flame to descend into the spout. After about 15 seconds, I successfully get a visible, milky cloud of vapor. The herb is now slightly "browned" but not "blackened". It's amazing to me how much heat is required to get a good cloud.
Despite the success, I still haven't figured it out completely. I even combusted a few times after that first success. Even after I changed to the upper position (on top of glass pinches) closer to the cap, I still had to use the same angle, with not much better results.
It's a shame there is only 1 vapo-bowl video on youtube, and the guy used a regular bic lighter, so it didn't really help me. I really hope I figure this out soon, because the lighter fluid is gonna be expensive. I had to fill up my lighter 3 times before I was feeling satisfactory effects!