I would do more than one watering worth of a flush. You want the plant to draw in the water and release it a couple times to really accomplish a good flushing. Distilled water is fine, as long as you're managing the PH. Other than that I am in favor of the darkness period, I have done it with some plants and haven't with others, and haven't really noticed any difference.. they're great no matter what, but like you said, it can't do any harm I don't think. Other than that, harvest when the trichs are to your liking. Personally I harvest a little bit earlier than the 50% amber trich schedule that a lot of people go with. I have found that when I harvest a little earlier, by the time its dried and cured a bit many more of the trichs are amber than when I harvested. So basically if I were to harvest at 50%, my final result would be 75% amber or so. Thats just my experience.

Then of course... enjoy smoking/consuming. Post some pics!