How to teach basic shomen suburi in 1 hour

1- The traditional, Japanese way
pick up a shinai, do like me.
Jogeiburi for 10 mins.
Men suburi for 10 mins.

2- Suggestion for more adapted way
Using bokken
Explain proper bokken etiquette
Start with footwork (suriashi back + forth), bokken behind back - 15 mins
Bokken grip, proper chudan kamae
Kamae + footwork (back + forth)
Follow the leader
Stationary, rotate shoulders, bokken up (forehead) and down (chudan)
Stationary, extend arms as coming down, to reach imaginary opponent
Add TeNoUchi
Explain KiKenTai-Ichi
Men san kyodo (1 arms up, 2 forward, 3 hit, 4 back)
5 times forward, 5 times back
After comfortable, Men ni kyodo (1 up + forward, 2 hit)
Finally, add Kiai.

2 hours of this is what it takes and is enough to establish a strong basis. It also gives them a good overview of all the fun stuff (short of hitting a real target). And they get a ton of exercises for home.