Well, you're close, Russo. Actually, I was the fireman, and as such, my left arm starred in the movie!
IIRC, Sid McKinney was engineer the first day of shooting. At any rate, we were ready at Lobato siding early in the morning and had to wait at the east end of the mainline for quite a while as the movie crew got set up. It was Fall (early October, I believe), and the morning was clear and quite chilly. Our first move was to run the train westbound into Weed City Station and stop the caboose at the platform. When we finally got the signal to go, the front end of the engine had cooled quite a lot from sitting still in the cold air for several hours. As we started and got up to speed, the stack spewed great clouds of white steam from all the condensate. The director loved it, and asked us to make that beautiful "white smoke" again the next take. We had a hard time explaining to him why we couldn't do it again and again.