Briefing
I always mention that aircraft engines are designed differently to car engines. Whilst aircraft engines are designed to be very reliable when running they are not necessary easy to start, unlike your car engine which will start at half a rotation. Always mention it before attempting to start up.
This tends to avoid any alarms if you need to "fight" the engine a bit to get it started.
I think I saw the tip on here and it's certainly calmed a few pax.