Some words or phrases have regional variations and everyone’s definition of humorous is going to be a little different. The best ones are probably R rated so I won’t list them here. Good luck with your project; here are a few that got my attention when I started work years ago:

Hook up those hose bags (connect the air hoses)

We have a kicker (car causing an undesired emergency during a service application)

Dump the air or pull the air or big hole it(duh!)

Stretch the train (pull out the slack)

The crew is dead or they are dead on their hours (over hours

Malfunction junction (screwed up yard or interchange point)

Hoghead (engineer)

Brownies, as in “I got 20 brownies for putting that box off the end of two track”. (points you score for mistakes. When you collected 60 you lost your job)

And always liked, “platform hustler”