I didn't want to steer the other thread too far away from it's subject so here's an answer as a new topic.If a radio transceiver is not deployed then what would you recommend as the best "workflow/camera/flash set up" for the Digital Rebel cameras (T3i, T4i...) please with a single or multiple non-Canon flash units?
(Note: My experience with this series of bodies is limited to the T3i, but I believe the situation is the same with other models)
With the "Digital Rebels" and flash there are basically two situations... one with "live-view" on, a second with live-view off.
With live-view on, the camera will not give a flash sync signal unless it senses a Canon (or Canon dedicated flash) attached and powered on, or, the built in flash is up and recycled. The work-around I use if I need to use flash from live view is to have one of my "official" Canon flashes connected to the camera via a remote flash cord with the flash positioned off to the side on a stand or sitting on the table. It is set to manual, either 1/64 or 1/128 power (with these external flash unit on “manual” there is no troublesome metering pre-flash, so basic optical slaves can be used). The flash units actually used to light the subject are then triggered by optical slaves (either ones built into the flash as with most Yougnuo units and some others, or with inexpensive eBay "hot-shoe" units). Unfortunately the built in flash with these cameras can't be set to a useful manual mode. Otherwise it would be a simple matter to set the in-camera flash to a low power manual setting to trip external flashes optically.
(BTW... some optical slaves are less sensitive than others. I know the one built into the first Yongnuo 460 flashes were not very sensitive (560’s are much more sensitive), so if you use this external manual flash technique you may need to adjust flash power setting and positioning until you get reliable triggering.
You can make use of the built-in flash, but no matter what settings you use there is always a metering pre-flash before the main flash. This will can fool many optical slave units (although some slave units and some of the the Yongnuo flashes have two optical slave positions... one that "ignores" the pre-flash). Because of the nature of the high magnification set-ups we typically use here, the internal flash will generally go off at full power. This will really drain the battery quickly and cause about a 3 second delay between shots waiting for recycle. Even though I use an AC power supply for the camera and the battery is not an issue, I don’t work this way since I already had a large Canon flash to set up on "manual" as described above. If you already have slaved flash units that will ignore the “pre-flash” and have an AC power adapter (or lots of batteries) It could be worth exploring further if you do not already have a separate Canon flash that can be set to low manual power settings. I would probably be a little leery of using it for very long stacks until it was ascertained that there was no real heat issue from such constant use. Most of the time you will want to scrim out the light from adding to your actual subject lighting.
When live-view if off, there is no real problem. A flash sync signal is given with each exposure. So you can “tap into” the camera hot-shoe in a variety of ways to trip flash units. I still use mirror lock-up so that two shutter "presses" are required... the first to lift the mirror and the second to take the picture. (Even though it's a flash exposure, I feel that anything I can do to reduce vibration, especially mirror movement is desirable.)