matthewgoodyear wrote:I would like to average 28kms a day
That's a adventurous ask for a first walk, but possible if your keen and fit. Some / most of the GNW would be fine but other sections will leave you very sore if it's your first big trip walking 28km's a day. There are some decent hills in the mix for you to wander over.
I did Somersby to Speers point in Sept last year. I just camped where I liked but you need to be mindful of your water sources. I just walked each day till I had enough and set up the hammock (The hammock was a godsend as I didn't need a flat campsite) . I think out of 3 nights I only had water on 1 next to me. The rest I had to pack the H2O and refill a few km's down the track. You need to have a good idea of where you are on the trail and where a spot is you can get water. Keep in mind a lot of the water from the creeks in Sydney I wouldn't drink at all.
I like to think of myself as reasonably fit and a fast walker. Hardest day for me was from Yarramalong to the comms tower above Congewai Valley West. Think it was something like 30kms and there are a few good ups and downs in that

. I was a sore boy by the end of that. Next day was 42kms and I was all but spent.
After that I was sore for a week but would do it again in a heartbeat.
I'd say go for it if you think you can but be prepared to add a few days.
If you have sore shin's keep training till you can do that and not be sore. Or do a walk like that 2 days in a row and see how you feel.
Are you going to lug the food for the whole trip ??
Resupplies are pretty easy if you have someone to meet you.
If you wanted to do a resupply on the north end of the watagans I'd be happy to help out (PM me if you like)
Are you camping the whole trip or doing the B&B thing a few nights where available, if you did that you could mail the B&B some food you could pick up for the next few days ??