For us sequencer-based composers:
Chordal voicings. E.g. Trombone block chords. Play your chords into a single ensemble track. Be careful not to use more notes than you have players (I have Tnr Tbn Solo, then Tnr Tbn plyr1 to 3, plus Bass1 and bass2).
Sort out any legato issues, or modulation in this clip.
Then copy the clip down to each other player. (SX users - make sure you don't use linked clips, otherwise your edits will apply to all copies of that clip. I use linked clips as a reflex, so this is hard habit to break).
From the top clip, delete all but the uppermost line.
From the second clip, delete all but the 2nd line.
Repeat until no clips remain.
Use ears to figure out any problems, change phrasing and modulation as required.
It's worth doing, to split the chords out like this, rather than leave them all played by one of the poly ensemble players, sounds really lovely! Works for trombon, trumpets, flutes, etc.etc.
Hope it works as well for you guys as it did for me.