Charlie just described beautifully the kind of switching that was common in the good old days. Trainmen and switchmen were really good at figuring this kind of thing out, using skill and ingenuity to make their jobs a bit easier and save extra moves or long shoves. On Cumbres they did a similar thing. When the last turn arrived at Cumbres the helper would cut off leaving the caboose just east of the summit (the helper would then duck into the short siding, run around the turn, and head for Alamosa, assuming it did not have to go back to Chama). The caboose would then be allowed to role down against the rear of the train on the mainline while the road engine added the additional cars off the long siding before continuing east. I wonder how much of this sort of thing still goes on. Just getting rid of the cabooses simplified a lot of moves.
JBWX