I had a few follow up questions to your advice to “just build a mix to an unused pair of Auxes.” I know that “aux” is short for auxillary. I assume that simply means the xlr output ports on the back of the mixer? Why a “pair”? Is it possible to set those up as Left and Right for stereo?
Glad to see others have jumped in to help in my absence (one of the things I like about this place!). Yes, two of them, one panned Left and another panned Right.
On the Expression, you'd hit an unused "Mix" button and raise each fader to its desired level (just like with monitors). Repeat for the 2nd Mix/Aux. Effects can be sent this way, too. Those Mix Output XLRs on the back would provide signal to your streaming gear.
Dave