You’re not alone, others have had similar confusion when placing the mouthpiece on / getting started.

In my opinion, Success in Largo Long tones has less to do about the setup of the lips than it does about learning to release the air and relax and focus on efficiency and obtaining the most resonant, full sound possible, letting your body and brain learn from the sound.

Your lips need to be inside the mouthpiece to obtain a resonant sound so don’t worry too much about the milk spout concept–in my opinion, that’s more useful as you get a little further up the staff into the middle register or begin slurring upwards and is more about what’s happening inside the mouthpiece than how you put your mouth onto/into the mouthpiece.

The key is to relax, release the air (don’t blow / “throw the arrow”) and the singing concept is really helpful and key–it really helps us understand how much air is required, which is much less than we anticipate.

I hope that helps, FWIW. Good luck–it is amazing how easy it is to play above the staff once we learn to relax and not to overblow. I find it helpful to me to think about how I want it to feel when playing, then focusing on that feeling and avoiding tensing up / tightening and prioritizing the feeling over hitting the note I’m trying to play–being willing to fail hitting the note (which hardly ever happens, actually, because it is much easier than we realize when we let go).