It depended on which era you were from. WW2 & Korean War vets drank on the job. Vietnam vets did pills, weed, and a little cocaine. That was just a cultural difference an old head told me when we talked about it. But if you didn't do something on the job people thought you were a narc.
That post about the 5 man crews is true, no doubt in my mind. I'm most familiar with former Frisco territories and a number of head end brakemen became proficient engineers "off the record" because they'd have to run the train to the terminal if the engineer and fireman were too drunk. Another old head said "the party began when you went on duty." Obviously, the guys in the caboose did the same.