To do back button focusing on the D4 it's about the same as other cameras.
CSM a1: AF-C priority selection = Release
CSM a4: AF Activation = AF-ON only (OFF)
CSM a8: Assign AF-ON button = AF-ON
Focusing mode to AF-C (continuous) using focus mode button on front camera and rear dial
Gary in SE Michigan, USA. Nikonians membership - My most important photographic investment, after the camera. D4, D810, D300 (720nm IR conversion), D90, F6, FM3a (black), FM2n (chrome) YashicaMat 124, Graflex Speed Graphic 4x5 My Nikonians Gallery & Our Chapter Gallery