For whatever reasons, I've been approached a lot about giving arranger lessons. I've tried to help some friends get started, but so far none of them has really had the "want to" enough to do much with it.
It seems SO simple to me but when you start teaching someone you realize that maybe it isn't so simple, because so many different skills are involved--timing, learning chords, learning notes, music theory, instrument emulations, learning the operating system. . . on and on. There are so many levels of arranger use. I mostly play the styles and comp with right hand. You can also use sequences, multi-track your own recordings, make your own styles, songs, sounds, again, on and on.
Both my younger sons took a couple years at Yamaha music school and learned a little, but neither was interested in pursuing it. They do, or did at the time, offer an excellent program. But it takes desire and perseverance, as does anything worthwhile.
The wonderful thing about playing arrangers is that you can enjoy them and benefit from playing them at just about ANY level. You don't have to be great to make music with them. Music should be FUN and playing it is GOOD for you, at whatever level.
Years ago I thought I was pretty good. Now I go back and listen to some of it and it was not very good. Now I am my own worst critic. Most of us are very slow to criticize how the others sound and are satisfied to encourage them. I have always welcomed criticism because I use it to learn and try to get better. I've been fortunate to have friends who will say things like "The right hand is too loud, the vocal is too loud, the sax guy didn't take a breath, that is not the way that song was written, you're playing the wrong chords, etc." All chances to improve and much appreciated by me.
It's a deep subject and I'm ready for breakfast after another long night of entertaining rich folks from Texas!
God bless 'em though, they keep me from having to get a real job.