5 pounds of flour, a couple pounds of salt, food coloring, water and 7 kids under 5. Sounds like a recipe for disaster but we survived.
I took about 110 shots edited down to 26 shooting with the left hand flash technique. It took a while to process that shoot because on the whole it between 0.5 and 1.5 stops underexposed and with the all the flash bouncing the color temperature was all over the map. I've got in the can now, so lets look at a couple shots.
First up a sample of a problem with the classic ceiling bounce. We have fairly high vaulted ceiling in our kitchen and I was taking pictures of short people so the bounce was necessarily coming from a rather high angle. The net result is the eyes are in shadow (sometimes called "raccoon eyes"). This is the problem bounce cards are supposed to solve. Personally I much prefer the look of putting the bounce point further back to lower the angle incident angle but a bounce card makes "good enough" much easier. For my taste the light with a fill card it often too flat so I try to avoid it when I can. Control over the bounce location is the primary reason I had the flash in my left hand but it didn't help me here. I don't remember why I chose a ceiling bounce for this shot (probably something blocking the curtain behind me).
Here is a similar shot where I did a better job directing the flash. I would have liked the light even lower, but the bounced light is coming in at a low enough angle that there is some light in the eyes--no bounce card needed.
The first two shots in this collection could have been done easily with the flash in the hot shoe and rotating the head. This one, with a wall bounce coming in from camera right, would be tricker. In portrait orientation I usually hold the camera from above which puts a shoe mounted flash on the left. Holding the camera from below would get you this shot but it is on the awkward side. One tool for solving this problem is a rotating flash bracket. The camera rotates while the flash sits still so you can always take full advantage of the flexibility of the flash head. The left hand flash technique solves this same problem with much less fiddling.
Finally, a shot that was only going to work with a left hand flash. Blocked on all sides, I saw that a wall bounce wasn't going to happen and a ceiling bounce certainly wasn't going to give me any useful light. Then I looked down--the table was white! The light coming from below gives this shot something of a surreal look but I like it better than the other option: direct flash.
Hand holding a flash gives a lot of flexibility in lighting and better yet it is quick. I can adjust the light position while I am framing the shot. The biggest downside I see to it for candid photography is having to handle the camera with one hand. That is doable with a small prime lens but would likely get unwieldy with a bigger zoom. In the long term I intend to pick up a flash bracket (probably from RSS) and hopefully with practice that will similar results and let me handle the camera with both hands. In the interim I'll be working more on my left hand flash.