A reasonable not too long warm-up, repeat short phrases of the programme no the whole piece, and think you are alone in the scene , or alternatively concentrate in only one person, and best, a friend of the public. You play for this person, nobody other.Think musically and technical only for breathing.
If you are in the middle of the piece and instrument need of be emptied of water but no time is available , you can take the horn position slighly a few degres up; the accumulation of water clear the vulnerable spots and the sound is recovered.That can help in this extremes situations for a short limited time.Of course,then with a couple of seconds available ,emptied the instrument as normal.
Daniel
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Schilke S42
Schilke C7
Olds A-10 Ambassador
Olds L-12 Flugelhorn