A great feature of the Canon EOS 70D is its wi-fi functionality. This means that I can practise taking portraits of myself via the EOS Remote iPhone app (before unleashing myself on willing volunteers). The app allows you to adjust the camera settings, as well as viewing pictures that you've just taken, meaning that I wasn't shuttling to and from the camera too much. The Face+Tracking mode (where the camera automatically tries to detect a face) seems to work well enough.
For my low key set-up I used a single Canon Speedlite 430EX II mounted on a stand, reflected off an umbrella, and shot against a black paper background.
One issue common to both the live view mode (using the LED screen rather than the viewfinder) and the iPhone app is that what you see on the screen is what you will get in the final image (without the flash). Crucially, the auto-focus uses this as well. But, with low key photography, you're trying to get rid of the ambient light, so the camera can't focus... The solution is to use exposure compensation in aperture priority mode, which will increase the shutter speed whilst leaving enough light getting to the app.
So, it's not quite as good as having someone else pose for me, but a useful start.