Allen-Heath XOne 9:2 is my mixer of choice. When I have guests, I turn the channel gains all the way up and all tone controls to +6 then play a few choice tunes. I set the processor input from there then turn everything on the mixer back down to normal. Once I see how well the guest controls their dynamics, I may provide more gain accordingly. Often, you see them turn everything up - especially the channel gain, bass and treble. At that point, the system is still well below red and the DJ has a lot of control over their tone and overall volume. There is still no compression or limiting anywhere in the system. It is rare anyone ever asks for more volume.