Ed,
I’m not sure how Greg will weigh in on this, but I’ll share some thoughts.
I share your experience with the first note inconsistency and insecurity. My personal analysis is that once the first note is played, the mind/body immediately adjusts to the appropriate embouchure and support to fix the problem. That’s great but it doesn’t help the initial attack!
I’ve been doing several things lately that have helped:
1. Blow THROUGH the note. Greg’s Arrrrticulation is great for this. His Response concept helps you establish that pure connected tone immediately following the attack.
2. As you inhale (body’s concert hall), position the embouchure with firm corners, WET YOUR LIPS WITH YOUR TONGUE to reduce friction of the air over the lips. That really helped me.
3. Have a firm and definitive tongue movement when releasing the air on the initial note. Don’t pussyfoot around!
4. Lastly, practice just making a single note entry (any note) and then pause a few seconds fully relaxing your embouchure and taking the trumpet away from your lips. Do that over and over and see how many notes you can attack cleanly in a row. Eventually your percentage will increase. Tick the box!
Hope this helps,
Pete