John,
I think you need to talk to George Gourlay (
http://www.grmbc.org.uk/). There is a simple and effective method which works for smaller scale and is cheap and safe (compared to the American BB firing mechanisms). It involves a heated wire.
[I have never understood how the Americans manage to hold these weekends where they fire thousands of BB pellets at each other in a society where someone sued Nike when she tripped over her own shoelace and won!]
This weekend is our Start of Season sail and while we traditionally put on a pyrotechnic display we had to stop it last year and will not be doing it this year either. Otherwise you could have come to see it on operation for yourself.
At the flick of a switch there is a flash and smoke, very effective.
James