[jpanderson80]

On the master fader, the SEND will show your Master output (hardware send). I think that on most interfaces, the SEND is defaulted to the 1 & 2 (That may be incorrect, but that's what I experienced. So, if you open a new reaper session you may see the output coming to 1&2 on your console.)

In Reaper, by default, the tracks are routed and summed digitally to the Master Fader. You can set the Master Fader SEND to any hardware channels. So, set your output to whichever channels you want. I use a stereo channel on the console, so that I can control the output with just one console fader and mute button. For Mastering, the SEND level coming out of Reaper will need to be about -18dBfs in order to hit your console at 0dBvu on whichever channels you've chosen. That sound goes through console and out to your monitors. I SOLO my console channel so that I can only hear the REAPER output.

To render the mixdown through the console, you'll have to set up a way to record what happens through the console. As stated in a previous post, I route the Console 2buss back into the console so that I can capture THAT channel into Reaper. (just be sure not to create a feedback loop!!!) It will record as a WAV file just like a normal recording session. If you have plugins on your Master buss as well, then render the MIXDOWN WAV file ITB.

To render during mastering, it'll be all ITB.

I've attached a chart of the workflow that I use for my console. I'm not 100% about your console. This is a personal preference decision AND your console routing.