I was up there a couple of weeks ago.
There are various paths along the broad ridge of Blea Rigg but they are not particularly clear.
The walk from Stickle Tarn to Sergeant Man is pretty straightforward IMO.
If the weather is clear you can see the destination for much of the way. Walk round the east side of the tarn then follow Bright Beck (the feeder stream) north until it forks - follow the east (right hand) branch due north for a mile or so and you're there.
If it's foggy, take a bearing and walk on the needle.
Much of the Blea Rigg ridge can be a bit wet underfoot but it's certainly not a marsh.
Just follow your nose and don't be too worried about paths - you'll be fine