I have found - it is not important wich asanas to teach and for how long keep holding there. Also I am a big fan of Iyengar style, in 1 hour classes (popular down-under) it is hard to teach that way - people say it's boring.
The story is very different if you do vinyasa style with beathing rithm...
That is : 4 count inhale, 4 counts wait, 6-8 counts exhale, 4 counts wait.
If you try Surya Namaskar like this:
arms up on inhale(4) extend up (wait, 4) arms down slow on exhale (6) wait (4) arching back and looking up on inhale (4) hands on shins or take bigtows, wait (4) ... and so on.
It is your call what to take for 1 count - 1 second or 1 heartbit.
2 rounds will warm me up on cold Wellington morning. After tird one I start to feel gastric fire...
It is difference to practice yoga and teach yoga to general public. This way is unusual for people and they start to pay more attension to the teacher, thinking "Hey, that's real yoga!". As for me it is a good way to make calss "click". Also it gives me some time to talk about safety and ways to engage into asana from very simple level to more complicated.