WTG
To add to what has been said before, hit the button a sec or two before you start mouth sucking, and continue sucking for a sec or two after letting go of the button.
The rationale behind this trick (for all devices). It takes a sec or two to start producing vapor, and produces vapor for a sec or so after the switch is let go. With this method you are sucking in less air.
Happy vaping!
Oh, a nice slow draw will produce more vapor than just sucking on it.