You can't. His best option is assigning the output to Bus 1-8, not ideal. I used the d8b live for a lot of years, and It was nice to have a graphic across the stereo buss but I had a rack of 12 dbx 31 band EQ's to do wedges.
If you had the open channels I suppose you could try and do something with channel patching where you take the fx return of the EQ and channel patch it to a channel then turn up the aux there.... It makes my head hurt thinking about it. The possibilities for eletronic feedback loops is great, I would probably abandon this idea upon further thought. Your best bet is external EQ.