I’m an amateur comeback player on this journey as well, so I don’t consider myself an authority, but FWIW, my understanding is that the top lip is most important. I have been having success the past couple months with “hiding the red” when setting the mouthpiece on my lips then moving my lips apart (top up and bottom down) as I get the lips and take a breath. I do the ooooh ahhh thing and check to see if I’m buzzing by pulling the mouthpiece out as I blow, etc. And my lips seem more forward than rolled in or tucked–I think I was doing that back in high school, in fact I recall being told to roll my bottom lip in or under as I ascended….which now doesn’t make sense to me.
That’s working for me. I’m having great sensations and my range and control is increasing, not out of strength or endurance but seemingly out of coordination of tightening the corners of the embouchure/aperture and arching my tongue in the back but getting the front of my tongue down and out of the way (I think I was putting the tip of my tongue too high and blocking the air column before) while trying to keep my throat open and relaxed. I’ve been thinking of it lately as patting my head and rubbing my stomach at the same time–kind of that focused effort of coordination, using my mind to actively control my different muscles in my mouth and throat (relaxed).
I’ve also been focusing on backing off the air and trying to use the minimum amount of movement necessary–I think I was doing way too much previously but the space between the notes as we ascend gets closer and closer, so it seems that less incremental movement would be needed the higher we ascend.
The only thing I would add, however, is that I have not been able to to play shallow mouthpieces (i.e. 3E) without bottoming out, but I have never in my life previously played shallow mouthpieces so I can’t say that what I’m doing is wrong. It feels and sounds good to me but I haven’t figured out how to play shallow mouthpieces yet.
My lips are on the thinner side and I went back to playing a 7C–I had moved to a 5C then 3C but things started falling apart on me so I decided to go back to basics and that’s working for me. But I’m eager to try out some shallower / brighter mouthpieces once I feel like playing has become more second nature / automatic to me.