Trevor dark's you take at the same exposure time as the lights, and as close as the you can to the temp of the lights, so ICNR here is a good option.
With your flats, they are not temp sensitive, and the exposure can be short, a fraction of a second, or let the camera decide on the AV setting, not the same times as the lights or dark's
Now for the amount, I usually take the same amount of dark's as I do the lights, that is because I us ICNR, and don't really have a choice here.
When it comes to the flats, about 10 to 12 is plenty.
Leon
