I have done Wondabyne Rail to Woy Woy a few times, lots of Black Cockatoos, amazing view from top of Wondabyne. I have not done from Patonga to Wondabyne as yet, will put it on the bucket list.
I too am looking at the sections further and scratching my head as to how to do them as a solo hiker. I have done Heaton Gap to Teralba - Catch the Rover Route 163 bus from Morisset Station to the Brunkerville BP. https://www.rovercoaches.com.au/client_ ... 747763.pdf
for the timetable and you need to inform the driver. If you drive park at Brunkerville BP there is options to go west/south and east/north towards Newcastle. If you don't have to walk every inch of the Great North Walk, avoid the section from Wakefield to Teralba, quarry trucks, poor shoulder and boring dangerous main road bashing.
Brunkerville BP can give access to the GNW heading South or be an exit point for a multi day walk from somewhere south heading North to Heatons Gap. I am yet to work out the nuts and bolts but thats what I would probably do. I have all so found that driving to a spot, walking to a campsite and returning back to car on same route while time consuming, may be a good option for me as a solo hiker. A route walked one way is different walking the opposite direction.