My local second-hand camera shop phoned me up the other day to say they had a vivitar 283 flash come in for £20. I was down there in a (pardon the pun) flash.
That gave me 2 flashes.. a vivitar 285 with a vari-power module (so I could set the power pretty accurately) and a 283 with a auto-thrystor. Now that's not much good so after a quick look at hiviz.com I went off to maplin and bought a 100k logarithmic pot and a small project box.
If you pull the auto-thrystor out of the front of the flash and plug the 100k pot in then you can VERY accurately control the power (and therefore the speed) of the flash. Then to make it all work nicely I tore apart the auto-thrystor unit, glued the plug on it to the project box and stuck the pot out the side and hey-presto an easily controlable flash unit :)
I plugged the 285 into a hot-shoe adaptor with a pass through and plugged the sync cable that came with the 283 into that. Then attached a momentary switch to the other side and went off to take some shots.
With 2 flashes you can have them behind the drops. A bit of frosted perspex behind them allows you to diffuse the light and you have wonderfully lit drops. However there was a problem. I was getting double images on every shot. The flashes were firing at different times :(
Seems that having the flashes in series, even with a short (40cm) wire between them was giving a noticable (not to the naked eye!) difference in timing.
So now I had to butcher the hot shoe adaptor and the sync cable and wire the flashes in parallel to the switch.. Success!!