Here's a photo I took of the walking in the wilderness sign when I was there a few years ago (Includes a contact number) if it helps.
I went one August, it was great walking weather. In regards to multi-day walks; There was a group who had headed out from the southern point (The gorge) for a through walk but I'm not sure on the details. There was evidence of campsites throughout the gorges along the Bynguano Range track as well.
I myself wandered (a bit aimlessly) about the Northern wilderness from the end of the Coach drive when I was there looking for dragons. It was easily the most alluring part of my time there. Really had a way of drawing you further in. Easy going, with many rocks to climb up (a few had phone reception too!). Endlessly pulling beastly bindie type plants (that are essentially caltrops) out of my boots was about the only hardship.
A few picsThe old NSW maps (on sixmaps) show a few tanks about the place, visible in sat images as well. Most pools of water I found in the gorges had dead animals (goats, wallabies) in them, and there was an incredible amount of goat droppings pretty much everywhere. But there was water nonetheless along with a few deep pools in the gorges. And that was after a pretty long dry period.