When alpha cutouts are the final goal Freemask firing another set of flashes to generate a mask during a 2nd exposure seems handy. - Is anybody using that technique and what would be a cheap way to automatically fire a different group of flashes each 2nd shot? I assume for my current setup I'd need to trigger 3 to 4 units in the first and at least 2 in the 2nd exposure, for the mask. So far I used a cheapo radio trigger with 2 receivers and relied on optical slave triggers for the other strobes. I'm using rails on the ceiling so sync cables between a trigger unit for the different groups and the flashes could be an option but I am open for inexpensive alternatives. Thanks in advance for any ideas and input.