I have 2 580's that I would like to string together to be fired off by 1 PW Plus2. I would appreciate someone pointing me in the right direction as to what I would need to string the 2 flashes and the PW and fire it off with the other PW on the camera.
If they're in close proximity (a few inches; on a light stick, for example) you can use a Y-cable to split the sync signal.
If they're further apart, you can plug an optical slave into one of them, and it will fire the Speedlite when it sees the flash of the other one. (Most optical slaves are NOT Canon-compatible. This one is: http://www.flashzebra.com/products/0272/index.shtml )
I find optical slaves are quite handy. I regularly use them in full sun, you just have to be more careful about placement. The one below is from Metz, works great.
Another option is a Lastolite Tri-Flash, in which you can mount two or three speedlites and plug one Pocket Wizard into a jack on the Tri-Flash and fire them all. The Tri-Flash performs like a regular umbrella adapter and mounts on a standard light stand. It ain't cheap, but it works well. Here's a link from B&H: http://www.bhphotovideo.com/c/product/741846-REG/Lastolite_LL_LA2455_TriFlash_Sync.html
Forgot to correct the name of the part: it's a Tri-Flash Sync, not just the Tri-Flash. The Sync is the part that works with the Pocket Wizard; to use a conventional Tri-Flash (without the sync capability), you'd need the splitter cables that everyone above has mentioned.
Instead of plugging your PW into the PC link socket link on your EXII. Plug you PW into an acc' HS. (if you're using an EXII, if not, then you will be using an accessory HS anyway).
Set the PW triggered 580 as your main, set your other 580 as slave. Mode on M, set your power levels and it all works.
PW into acc' HS ...
Another view ...
Set this PW'd 580 as your main flash as you would using the Canon system ...
The master flash is being illuminated with a Slaved 580 which is picking up the usual Canon IR signal ...
If you use TTL/ETTL you are going to have a FULL power flash as there are no camera readings for the TTL to work out.
When I had only two PW, I use to fire 3 580s and a 550 this way. Works fine with all the usual line of sight considerations.
