Just completed the Northern Circuit in 3 nights / 4 days. It was meant to be 4 nights / 5 days but the flies and heat and mozzies were so relentless I'd had enough by yesterday afternoon and decided to walk the last 6km of management trail - into the sunset from dramatic effect.
First day / night. Began walking at around 2pm from Five Mile Road Carpark. Took me 3 hours to arrive to West Barry Creek Camp. The track to West Barry Creek Campsite is good for most the way. I found it difficult to follow the track for the last km or so, I don't believe it has been tagged for a while and there isn't always a marker to lead you in the exact direction so you are left navigating to the campsite yourself. Since the creek drops down about 20 meters it's difficult to see the campsite from the top of the ridge. Barry creek is still running moderately, but there are a few stale pools of water so do what you have to do to drink safely. Campsite is nice amongst the trees, lots of mozzies at night which are always keen for a human to feast on.
Second day / night: Chinaman Swamp / Chinaman Long Beach: This day was interesting! Out of West Barry Creek Campsite the path is easy to follow once you hit the swamp / lowland area. It is relatively dry but there are pockets of track where you'll be up to your shins in water. I could imagine in the wetter months you could be much deeper! Don't rely on navigation markers. I was using my GPS and Map and still found myself at times stopping every few meters and backtracking just to find a way through. According to the wildlife officer down there the track was re-tagged 3-4 months ago. I couldn't follow any path (which he reassured me it is very difficult to even find it), so a lot of swamp bashing, and bush bashing is required. Fallen trees, overgrown bushes, heavy water logged boots, I found myself following a track which turned into a game trail, and ended up just walking in the direction of the beach with occasional reference to map to make sure I wasn't going in the wrong direction.
By the time I reached Chinaman Long Beach the walking obviously becomes much easier, but the flies were relentless. The 1.8km path from the beach to Tin Mine Cove in parts is heavily overgrown, but there shouldn't be any issues. Tin Mine Cover water supply is down to a very small stream, without rain in the next week or so I wouldn't be relying on water being there. Lovely sunset on the rocks.
Third day / Night: Walking from Tin Mine Cove to Johnny Souey Campsite: All straight forward. Track going from the Chinaman Long Beach to Three Mile Beach is well defined, some parts of the old 4WD Track are heavily overgrown but still easy to follow. Bumped into my first brown snake there, he was startled to see me and slithered away in a fast and efficient manner. Three Mile Beach is as you would expect, beautiful beach with rolling waves, only issue I had today was the overland pass before Johnny Souey Beach, struggled to find path but managed to work my way through to Johnny Souey. Johnny Souey Campground water stream is down to a trickle, again, without significant rain I would not be relying on this water source in the next couple of weeks or so - there is also another creek maybe 100m up from the campsite on the beach, but I am not sure if that it is fresh water or salt water from high tide because I didn't check.
Final Day: Track from Johnny Souey to Five Mile Beach is well marked and easy to follow, only one creek crossing which at low tide is very easy to pass. Biggest challenge today was the temperature and flies. I began walking at 6AM and arrived at Barry Creek at 11:30AM. After lying in my tent throughout the heat of the day to avoid flies, I decided to walk the last 6km and go home at around 6:30pm. I had had enough of the flies, mozzies, and drinking half my body weight in water to maintain hydrated.
If anyone has any specific questions about the track feel free to ask and I'll try and answer

Things I learnt. Don't underestimate the environment, don't overestimate your ability, always take too much water, don't wear shorts or a t-shirt, pants and a shirt will go a long way... and ask yourself what you learnt at the end of every day

Jickham