In my grow I used rock wool and I watered (and fed) my plants about every 2 days. These were two 6" cubes stacked on top of each other then placed on a bed of hydroton pellets. I gave them probably close to a quart every other day. I would pick up the cubes to test the weight and see how dry it was; that was a good way to judge. Also, get some panda film covers for your cubes; they will almost entirely eliminate algae from growing. algae will rob your plants of the nutrients they need. As far as nuting goes, don't nute them at all for the first two weeks then use 1/4 strength for another two weeks, then half strength for a week, then 3/4 for a week. Watch carefully for nute burn; that's the easiest and most common mistake for new growers to make.