We walked Harter and Green Crag as one walk and did Hard Knott separately as an out and back from the pass.
For Harter we parked at Branthwaite Biridge (marked on the OS map near Hinning House) after heading down the Duddon Valley from Cockley Beck. It was a very sweet remote car park by a stream and I could have sat all day there having a brew and reading.
Anyway the walk - crossed the Beck and took the paths through the woods to get to the direct path onto Harter Fell up via Mart Crag and Maiden Castle. From there the obvious route down to the valley then up onto Green Crag via the route shown on Dave's gpx trace i.e. Skirting around Long Crag.
Descent was via Grassguards Gill so I assume we came off the back of Green Crag and found the marked route down. And then followed forest oaths back to the car.
Probably not much help, but we had an enjoyable walk that wasn't too strenuous or boggy or route findings tense!
It's lovely over that way - remote and I just love the Dudfon Valley.
Hope you find a route and post a TR.