I'm personally not a big fan of what they call "line of sight" methods for firing flash (where the only way your off-camera flash actually fires is if the sensor on the flash sees a pulse of light from one of your other flashes). The reason I don't like this method is because it doesn't work consistently. Well, it works fairly consistently if your flash has a clear, unobstructed view of the other flash, but in real life, that often isn't the case (now, if you're thinking, "But, I've seen Joe McNally do that," that's not a fair defense for two reasons:  we're not Joe McNally, and  Joe is a magical unicorn of off-camera flash, and I think his flashes fire simply out of respect, fear, or both). Anyway, to keep from pulling out your hair on location, I always recommend using a radio wireless remote, which pretty much always works (even if it's hidden from view, and even if it's 200 feet away from you). However, using just standard wireless units, like the PocketWizard Plus II, you can only wirelessly fire your hot shoe flash—you can't control the power settings (which is the one big advantage of the built-in, line-of-sight method—you can control each flash's power separately). PocketWizard, though, introduced a new, small, radio wireless controller called the AC3 ZoneController, which lets you not only fire, but control the power of up to three flashes individually (it's the dream baby—the dream!). Just so you know, you need the AC3 unit, which sits on the hot shoe mount on top of your camera and controls everything, and then you need a receiver (like the FlexTT5 Radio Slave Transmitter) on each wireless flash you want to use (I didn't say it was cheap, I said it was "the dream").