Johnny, I'll give it a try. See if this makes any since to you:
in the course of playing a tune, you will have a run of pushing notes followed by a run of pulling notes. If you had a guitar accompanying you, this change of bellow direction would dictate a chord change on the guitar. The air button is used to "recover" to a desired bellow position. In other words, you set yourself up for the next "run". Using the Love Bridge Waltz as an example, the first run of notes is pulling. the next run is pushing. So, on the last few pulling notes of the first run, open the air button to recover the bellow to a more open position,and let off at the beginning of the pushing run. I always felt like it was more important to know when to let off, rather than when to open the air valve. Facts is, I probably play with it "cracked open" through the whole tune and only fully open it and let off of it at key times. If you haven't been explained this before, that air valve is a "shock suppressor" for the reeds. It takes a lot of the shock off when playing a "loud" note, if that makes since to you. It takes just a little while to develop the feel of using the air button, but once you get it, it will come natural to you. It's just like singing. You have to know when to catch a breath in between lines.
Hope this helps.
Jude