Hi Faded,
The reason it says nothing about timing is because the air pumps run 24/7, so whats there to say about that. Since you will always have roots that are in the medium, and growing down to the solution if they dry out your screwed. I recomend getting a better air pump, as the one that comes with the wf is cheap and terrible, here's the one I use;
http://www.altgarden.com/hydroponics-testing/air-pumps/dual-diaphragm-air-pump.html
As for rock wool, I can't help you as all of my grows are from seed and once germinated go straight in to the hydroton with no other medium.
I have a 1 plant stealth cab, I leave the fans and pumps on 24/7, veg for 4 weeks (or until the plant hits the screen), weave for 3 weeks, trim lower growth for 2 weeks (trimming anything below the screen, starting with the second week of flower).
I add solution every day and check pH and PPM, and change out the solution for fresh once a week. Right now I have an Reserva Privada OG #18, 17 days into flower, and it drinks about a 1/2 - 3/4 gallon a day with steady nute uptake (water goes down PPMs stay the same, to me thats the key).
Adding an airstone will likely cause your pH to rise daily, so it's very important that you stay on top of that or you might get nute lock out. But, I attribute adding an airstone to getting bigger buds and faster growth.
Do yourself a favor and read that scottyballs thread from start to finish, you will be amazed.
GoLdD