If you have a test lab, a good thing would be to setup a
complete functional network. Show the engineer how it's configured. Then
have them leave the room and then break it. Send them back in to look at
what is wrong. As they move through the process, help them by guiding
them through the troubleshooting process in a mentoring fashion, help
them analyze and break apart the problem.
"Visionary people, are visionary, partly because of the great many
things they never get to see." - Larry Pingree