Hey Ryan, the “Milk Spout” idea, the finger nail between the teeth and aperture corners in is a way to find something approximating the ideal gap. I used to have this issue BIG TIME!
Finding the SHAPE after ascending is one of the trickiest challenges of playing the horn. If you think mathematically/mechanically about this, each note has it’s own SHAPE so therefore changing between the two SHAPE’s should be easy… “Look How Easy It Isnt” (John Wooden, famous basketball coach!)
Familiarity and repetition whilst maintaining freedom and fluidity is the challenge that we all face. Don’t be down on yourself, this is the process of learning.
Start with small intervals, EYES CLOSED, and be sure that you are centering the lower note; and I’m talking playing an interval of a minor 2nd, 2nd, minor 3rd etc etc. Gradual development of SHAPE awareness will develop.