If I want to use the flash at it's most basic, essentially as the missing pop-up flash from my old 400D, presumably I would just leave it in ETTL and click away? I can then work my way into more sophisticated scenarios.
This is a good setup if you need the flash just to add a little light.
ETTL will also adjust to a bounced flash, so you don't have to think about how much light this wall/ceiling/reflector will eat up.
The "drawback" is that you are still using Av.
If you are in a very dark place, the exposure will lengthen and you might get blurry shots.
The flash will freeze parts of the image, but you still get the smear of the long exposure.
Two possible scenarios:
1) leave the long exposure as it is and set the flash to rear curtain sync.
This way the flash freezes the last moment of the exposure and you get some nice effect. Good for moving subjects, dancing, etc.
2) switch to M and let the flash compensate the exposure.
Even for the first scenario, I choose M, because I want to have full control.
I do landscapes (which are unlikely to need a flash)
Are you sure?http://strobist.blogspot.de/2011/09/mike-kelley-two-speedlight.htmlhttps://www.youtube.com/watch?v=riTVghtbQ7Ehttp://fstoppers.com/how-to-use-a-flash-with-a-drone-helicopter