Great tread Alex!
I play different brass (+ classical guitar and flutes). I love to take lessons and the latest I took from was a french horn player. Unfortunately she has moved so I should perhaps get another one. The lessons were like this: She showed me some of her tricks,etc., then we played duets.
Also going to different masterclasses can be great. I often get more from french horn, tuba, etc. (than trumpet). I get to hear new music, get other types of ideas etc., etc. Sometimes it can be rather boring to hear 4 or 5 rounds of Honneger's: Intrada at a trumpet masterclass.
It is also fun to know that there are a lot of other theories about brass playing than the one Farkas developed. Btw, french horn players still tend to be very into that thinking
I also love to watch TV where great musicians are teaching/playing - whatever instrument. Two days ago I saw a great program about the incredible singer, Bobby McFerrin (a Canadian documentary)
Ole