Hi --
Welcome to the forum!
I can't call myself a jazzer, but play soul, funk, pop. I have a regular church gig that runs the gamut from traditional to contemporary hymns.
I don't have formal training, but have listened to a lot of music and read many article about orchestration. That has given me starting points for voice choice and combination. Listening to real players (woodwind, string, brass) helped me to learn about the most common articulations. Then, it's practice, practice, practice.
The most important tool is my ears. What sounds appropriate, tasteful, musical? I probably go through 10 or more clunkers for every voice combination that works. I keep everything and delete clunkers when I think I have moved past them (i.e., not a valid starting point any longer). Overall, a critical ear is important.
As to left hand, I turn down the volume on my left hand. There seems to be enough musical "activity" in a typical style without the left hand making things muddy. Some pro players suggest turning off style parts -- maybe strip everything down to drum and bass!
Hope these thoughts are helpful -- pj