I'm watching an old California PBS show (don't ask) about a Tuba Christmas... convention? concert thing, and they were talking to this kid who'd been a trumpet player until he got braces when he switched to tuba (the mouthpieces are bigger, so they do better with braces), and AS a former trumpet player who had braces while playing,
ahem... apologies. I have some trauma from band teachers yelling, "Just use more wax!!" when I needed a break, and from orthodontists telling me I was ruining their work.
WHAT??? The wax just pressed straight into the brackets while you played, and there's no TIME during a concert to put more on between songs. So you just play. And you press that brass into the metal with your lips between and you're done.
The website we review applications on is down, and I just keep watching emails from applicants come in :| I can do nothing to answer your "what can i do to improve" questions friends I'm sorry.