G'day RW1,
Good point about the HEEDS. We have not started using them in our courses yet but I believe one of the lifejacket manufacturers has one of these systems incorporated. Not sure about 5 - 7 minutes with these systems, more likely 2 minutes but I could be wrong.
The biggest thing IMO if briefing pax is the same as for flight crew: Know the thing IS going to roll over if it has the room, and to have a reference point selected, grab it and hold onto it. Remain calm.
A good training video on helicopter abandonment is produced by Moxi Media. We use it in our training courses. It is well produced and it gives some really good information.