I try to hold in battery until I see vapor while looking down the glass stem then slowly inhale but I never know how fast/slow to inhale.
Ya, that's the downside to a lot of vapes, there's definitely a technique. Especially with the MFLB, that requires the most feel. Watch the videos on the Magic Flight website, they explain it pretty well. You basically barely want to breathe in, just super slowly sip in the vapor. That's the beauty of bag vapes like the Volcano. You can just inhale however you please! Even with the Pax, which is often touted as being extremely easy to use, I've still had to develop a bit of a feel for the best speed for drawing. The other issue is that once I'm pretty high it's tough to realize how fast I'm drawing! Hahaha. But ya, really the only way is to experiment and research and you'll figure out how to make it work the best for you.