From Whetstone Gate, it's often easier depending on the conditions underfoot to track along the path immediately to the south of the wall, hop over the stiley/fence thing at the end by the plantation (felling that bit, just now) and stick close to the wall until it goes around the angle, then take the clearly visible path which leads straight down to Piper's Crag (heading north).
I'm fine with the moor bit, really should recce the Chevin end...