In the East Coast standard gauge world, I was recently reading some reminiscences of a retired LIRR engineer named Mark Smith who had worked steam in the late 1940s and early 1950s. After returning home from the Army in 1945 he fired for a few years before qualifying as an engineer, and soon found himself called off the extra list to run helpers on the long "hauler" freights that would shuttle between Yard A and Holban Yard in Queens, New York, which in the eastbound direction required climbing the LIRR's ruling grade at Mount Olivet in Maspeth. (Yes that's right, the LIRR had helper territory within the limits of New York City.)
Smith admits he had no idea what he was doing at first, but says he soon figured out that the key to the job was to listen to the stack of the road engine, and then match it with his own.
Mark Smith: Climbing Mt. Olivet
Here's a 1937 Frank Reschke photo of a LIRR helper on Mount Olivet:
-Philip Marshall