Judging by the fact the engie used it twice and got stabbed, use something like skype for warning about that.
Swap the Tele exit and Entrance for a more enjoyable time, telling your friend when to use it as people think it's an entrance and getting a telefrag
Move it closer to an edge and swap spy for pyro dispenser for engie, make sentry, destroy it, pyro gets metal taunt laugh for extra effect
Spy camping it is always dangerous as it takes a bit of luck, like the demo, to turn before the stab and you can be cleared out no problem
Other games to play solo are pretending to be a spy to teammates (back up constantly watching them) and dispenser surfing (stand on enemy dispensers for as long as possible)