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Without question, the best way to learn how to arrange is to put in the work transcribing some of your favorite arrangers and dissecting the way they approach things.
Study the chord progressions they use and analyze their voicing. Break down how they use counterpoint vs. countermelody. Pay attention to how they use every single voice, common articulations, and where in the range do they have each part "live" (1st vs. 2nd vs 3rd).
Write down what you observe about how they do things, try to put it into words. Compare/contrast between arrangers. This will help you better internalize what they are doing and help you to find your own style.
Before doing any of this, however, I suggest to read, read, read. Here are a few books to get your started:
The Study of Counterpoint - Johann Joseph Fux
Contemporary Counterpoint: Theory & Application - Beth Denisch
Guide to the Practical Study of Harmony - Peter Ilyitch Tchaikovsky
Principles of Orchestration - Nikolay Rimsky-Korsakov
Essential Dictionary of Orchestration - Dave Black & Tom Gerou
Treatise on Instrumentation - Hector Berlioz & Richard Strauss
Arranging for Horns - Jerry Gates
Another excellent resource is Bandestration - https://bandestration.com/
Another great read that is HIGHLY applicable to writing for marching music is:
Fundamentals of Musical Acoustics
If you are interested to explore interplay between wind/percussion arranging and electronics:
Acoustic and MIDI Orchestration for the Contemporary Composer - Andrea Pejrolo