Do the aah-ooh. You have corner tension and there should be space between your upper teen and lower.
Do like Greg and release the air into a tissue held in front of you.
The lips are not buzzing. Do it again putting the mouthpiece to your lips.
Try backing off the pressure using just your mouthpiece held by the fingers of your non-dominate hand. Also angling the mouthpiece either up or down may create buzzing.
Your goal is not to be totally tensionless. Your goal is to learn the shape of each note without pinching the lips in the middle and gripping your abdominal muscles and closing down your throat.
Your lips buzzing may not be a bad thing.
I believe the idea of freedom is not anti-buzzing it is getting rid of inappropriate tensions. Learning when to play passive and active breath.
Don’t let the idea of your lips buzzing stop you with your training. Use your minds magnifying lens to find where you can get rid of unnecessary tension. Being aware of what you are doing can feel awkward, be careful to not obsess over it. Be aware while doing WindWorks, but spend some time playing only to make music and concentrate only on the music.