Welcome to 420 Cablelayer, glad to have you here with us. In this area
THE GROW ROOM - 420 Magazine you'll find answers to those questions, and many more you don't know you have yet. I'm a converted outdoor grower, now on my second hydro grow, and it helped me alot, as did the sound advice of several experienced growers.
Sorry to here about the RD. I have five femmed RD from Barney's myself in my seed collection.
Flushing is a broad topic. Are you flushing because of a problem, or finishing the crop? At any rate, you do it the same...pure, ph adjusted r/o or distilled water for a period of 3-5 days at which time you harvest, or ease them back into the nute program.
Flushing at the end is to clear nutes out of the plant and improve the taste/burn quality of the finished product.
It is more or less an accepted fact that hydro is faster than soil, but the speed increase in hydro seems to be a bit strain specific. Some like it more than others. I think a 1-3 week gain is a reasonable expectation.