Dogrobber, when I took a boating safety class in May of 2000 the Coast Guard Auxilry Flotilla 76 went over how to opertate an extinguisher on a boat. They covered the finer points of galley fires or below deck fires, fuel fires ect. I found the information to be very helpful
I am surprised you have not had more responces to this important topic. It is not just a stand back and blast deal.
As a business owner after a decent little fire that cost me about $10,000 I was sure to train my employees but only after it cost me money

It was just amazing how under pressure a tech can just freeze and act stupid. lesson learned.
Thanks for bringing this up. BTW I carry two ext's on my 23' Trophy.