In my experience, it works best when I place the MP on my face in a relaxed, natural position.
The AahhhOoohhh thing is really about engaging the corners. I tend to think of that more now than actually say / form that position with my lips–I dont believe WindWorks is about that.
You simply want to release the air through your lips, keeping the lips as relaxed as possible while still maintaining enough engagement of the facial muscles surrounding the lips to keep a seal on the MP. Less is more.
I have been experiencing this a lot lately, trying to develop my control of my increased range.
It has been amazing lately how little I need to do to achieve the pitches above the staff.
I believe I was really getting in my own way a lot, trying to tense my lips before attempting a pitch above the staff.
I have been focusing on relaxing and being willing to miss or crack the note I’m attempting, to the point that I was almost trying to miss to see how little effort is really required–ironically, when doing that I started hitting notes higher than what I was aiming for!
We want the lips to interact with the air like the vocal chords.
The only engagement we want is to reduce the aperture by engaging the aperture corners, which pushes the lips forward towards the mouthpiece.
I would try to avoid rolling the lips in or out, its not about that. Its about reducing the size of the aperture as we ascend while keeping the lips as relaxed as possible by engaging only as much as necessary to keep a seal on the mouthpiece.
The tongue arch is helpful and important as well.
That’s my opinion / interpretation, FWIW. Hope it helps.