I'm sure you will get some well informed answers to this one, John But, number one factor is knowing the road. In my day, the fireman learned by watching and asking questions and then running the engine under the watchful eye of the engineer. All steam engines seemed to have personalities of their own which added to the variables envolved. An over simplified answer to the determining the best cut-off position of the reverse lever was to hook it up until the engine started to grow weak and then go forward one notch. Handling of the air brake, both automatic and independent, was the big factor in stopping. This came by practice and experience.
Les Clark