Hi Flying Bull,
Are the firecrew that you mention already trained up to deal with aviation firefighting, but only used to dealing with fixed wing? Or are you going to have to start with the very basics?
The best approach for either situation would probably be to have some professional training conducted - better results and relieves you of any responsibility should anything going wrong
.
Otherwise I would suggest just giving them a basic safety brief on each heli type, and encourage them to keep their knowledge up with some further occasional visits. If need be, take some photos of the aircraft and stick some arrows on to relevant areas.
FFF