Speedlight setup for 7d and other settings

Question

So I'm very new to "action photography" specific to radio controlled cars. I have a canon 7D. I have learned how to set the c1-c3 to custom settings. For now I use the green "square" setting for group photo's and still "shop" photo's. I'm perfectly happy for now with the results my 7d produces in respect to those photo's. I just got the YONGNUO speedlite today. Here are the constants of my shooting:
1. Warehouse type lighting(not good especially when setting the apeture speed to about 1000) dark photo's.
2. the next few months (until spring) will be same setting
I want to set c1-c3 to cover action shots within a range of these poorly lighted facilitys
so any suggestions on what I shoudl set them too and what the best settings I should set my speedlight to???
thanks again, this is one of the best forums I have ever been to for ANY subject
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Answer 1

I don't have a Yongnuo flash. I use a bunch of Canon 550EX and 580EX II flashes and am most familiar with them. So the following may or may not be exactly what you can do with your flash... But it's what I'd do with my flashes.
A flash can be used in a warehouse lighting situation, so long as you are just trying to illuminate a specific item and not the entire warehouse. I suspect you won't be able to bounce the flash off ceiling or walls, so will probably need to direct it right at your subject. That may or may not give you the results you want. But, what the heck, give it a try and see if the results are what you wanted...
If you are using a longer telephoto lens, you might also need a flash extender to concentrate the light farther away. Most flashes are designed for up to about 100 or 135mm. Using 200mm or 300mm lens with them might be unsatisfactory without an extender (link is to the only one I found quickly that's specifically for Yongnuo flashes, you might shop around... I use a different type for my Canon flashes). A flash extender can bump lighting strength by 2 or 3 stops at a typical telephoto distances.
Now try this...
Set your camera to 1/250 shutter speed, manual mode (M), and put the flash in ETTL. You control the reach (distance) of the flash with the lens aperture... the larger aperture, the farther the flash will reach. Use a smaller aperture for closer distances, to prevent blowing out images. Turn off Auto ISO. Set your camera's ISO a bit below what it would need to record the ambient light with the shutter speed and aperture combo you're using. At the same time, be aware that the higher the ISO you use also increases the flash's effective reach at any given aperture. You have to strike a balance, where you get the reach you need but keep the ISO low enough to make the flash the primary or main (or only) light source.
Using M makes the flash the main light source, as far as the camera is concerned. ETTL will still provide auto exposure, even though the camera is set to M with Auto ISO turned off. Using flash as the primary light source (overpowering the ambient lighting), will eliminate most or all problems with the color of mixed lighting. Use the "Flash" white balance setting on your camera (it might do it automatically if left in Auto White Balance, once the camera senses a flash is being used).
You can still use Flash Exposure Compensation to increase or decrease the exposures you're getting.
The main reason to set up this way is that the flash will act like a relatively fast shutter speed, around 1/720 is typical with most flashes. That will freeze relatively fast action. You could even slow the camera's shutter down to 1/200, 1/160, 1/125, 1/60... It would matter because the camera's shutter speed doesn't really determine the exposure, so long as it's not so slow that ambient light starts to be recorded. In other words, the flash is acting like a shutter, instead of the camera's shutter.  
If some ambient light is still being recorded, you can see some odd (or interesting) ghosting effects. You have a choice... set the flash to rear curtain sync so that the ghosting "trails" the subject and looks more realistic.... or you can  decrease your ISO, so that less ambient light is being recorded at your chosen aperture and shutter speed.  (Note: You cannot use rear curtain sync and HSS at the same time, see below.) 
If the flash itself isn't fast enough to freeze the action, you will have no choice but to use High Speed Sync (HSS). That's usually set on the flash itself and it seriously limits the distance your flash can reach, but allows you to bump up your shutter speed to better freeze action... to be able to get enough reach, use the lowest shutter speed you can.... try around 1/800 or 1/1000, 1/1250... the faster your shutter speed, the less reach of the flash. 
Unless you shoot in the same location frequently, the lighting there is very consistent and you want the same sort of results all the time, you may or may not be able to use one of the presets (C1, C2, C3) the way you're trying to do.
Be sure to turn off Auto ISO. And do not use any of the camera's auto exposure modes (Av, Tv, P). Those will force the flash to FILL mode, and try to expose based on the ambient light as the main source. You'll get too slow shutter speeds, or too shallow depth of field due to too large an aperture, or too high an ISO
Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7D(x2), 50D(x3), some other cameras, various lenses & accessories
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