Past Devoke is OK, but has some very wet sections. The Waberthwaite bits I’ve not done, but don’t underestimate how long these can take and I’d guess it will be indistinct and tussocky grass. never heard locals talk of it.
Better to try to work in the trails through Broughton Moor forestry and Stephenson Ground to the Duddon valley. Coming off Walna to Coniston, turn right down through the quarries past Tranearth, to Torver (Wilson Arms for mid ride refreshment). From there along the road, up the steeep road and into the forest. Climb up along the forest road following the true left bank of the River Lickle, cross the river/beck and ride the lovely singletrack down the right bank of the river. Continue to Stephenson Ground, Carter Ground, Stainton Ground to Kiln Bank and down the BW down to Seathwaite (good pub). Start/finish in Seathwaite would be a good plan.