I was there last winter and did the walk over three days.
Bittangabee campground was fine. So was Saltwater (but both require bookings). They may be closed after recent rains - Parks NSW website should explain in the alerts. If you do stay at Bittangabee, you can reserve campsites away from the vehicles, which I would recommend for hikers.
There is a small campground at Leatherjacket Bay, but it isn't very far into the walk. Mowarry Point is the pick of the bunch and a better distance for day 1.
Hegarty's was closed with no structures left and really serious regrowth. It looked like it had been reclaimed by the bush after the fires. You wouldn't be able to find a spot for a tent if you tried while we were there.
Here's a write up of the trip with pics of all the campsites:
https://www.randomfootprints.com/single ... mbat-talesCheers and good luck! It's an awesome part of the world and well worth taking your time over three days to enjoy it.