How often to water, and when to flush??

[greenpassion]

I am totally new to S/H and have questions... I have just put my phals and oncidiums into S/H, using hydroton. I have them in clear glass vases that I drilled holes about an inch from the bottom. I am reading here about flushing, and am wondering if I should should be doing this. When and how often? Also, do I keep water in the reservior at all times? I can see roots in there, but it looks like no new ones. And what rooting hormone should I get?