Had a chance to work on my throwaway flashes from disposable cameras.
Learned a few things.
First, six disposable flashes in parallel draw a lot of current!
The flashes were charging up too slowly off a single 1.5V AA battery, so I decided to use a 6V gel cell I had lying around. Of course I had to somehow reduce the 6V to around 1.5V so that my flashes don't explode. My "solution" was six 1N4001 diodes in series; their forward voltage drop equals 4.2V, which brings down the gel cell's 6V to a safer 1.8V. Close enough.
What I noticed (the diode string is at the bottom-left of the picture) is that while the flashes were charging, smoke would emerge from the diode string! turns out the solder joints were melting!
To Dennis: now we know where the energy lost in the diode forward voltage drop goes. It becomes heat! lots of heat!
Bad news, I paralleled the triggers on all the flashes, and shorting it to ground only fired one of the flashes. I think the flashes have to be triggered separately.
Which means this article in DIY Photography, which so optimistically shows the flash triggers in parallel, is wrong.
OTOH, the article does mention you may need more than one slave. Oh well.