Hey Jim, without seeing you, it is a little difficult to say BUT imagine the full balloon i.e. full lungs, can you sit there and after taking a full breath, seal the mouth either at the lips or with the tongue so the air cannot escape? IF so, do this and totally let go of any contraction in the air support muscles. The air still want to come out.
I want you to recognise that feeling of the air right at the lips or the tongue. Quite a bit of pressure can build up purely because of the elasticity in the system. When you then open the lips or lower the tongue, there is a small explosion of air. It won’t last long but that is OK, you are not playing the horn yet. Just get familiar with the feeling of the build up and release. DANGER: Watch out for closure in the throat doing this!!!
NOW, experiment with your voice. Full lungs and hum a note. How much sound can you get from using Passive Reduction? Work on getting more sound by letting go in the body.
I want you to play as freely as when you sing i.e. I want the lips to interact with the air as if they are the vocal cords.
Have a play around with that.