We usually plan our trips so that on various legs, we will switch. So, from Durango to Rockwood one fireman will work the grade. At Rockwood, we will usually change fireman and give him a break. Working that 2 1/2 % grade is no easy task. From Rockwood to Cascade will usually be another fireman. Cascade to Needleton will be another rotation, and the Neeldleton to Silverton is yet another. There are usually a minimum of 3 guys on board the train who will fire. One will rotate with me in running the locomotive. Two fireman would probably be all you need to go all the way to Silverton, but then we are doing this to enjoy ourselves and not have a heart attack.
As for the people actually up in the cab during a run, it is usually four: Engineer, fireman, wood passer and pilot. We have found that having a wood passer is an absolute necessity. No fireman can run back and forth from the cab to the tender and keep the flow of wood moving with sufficient speed to keep the engine going at a good clip. The fireman is also responsible for keeping the water up, so the fireman literally has his hands full. The cab on Eureka while going up the mountain is a very busy place.