When I aquired my first plant (in rockwool) I had no clue what to do with it. A man working at a local hydroponic store told me not to water until the top was dry and crusty??!!(that is wrong needless to say). Fortunately I found help on the Internet and eventually stumbled into MP. My plant didn't die,:yay: thanks MarijuanaPassion
whodat, keep listening to people like PCduck, you'll do fine.
Hydro is always wet. You don't need a moisture meter. Water level indicator ...maybe, it depends on what you do with your plant in the rockwool. There's waterfarms, ebb and flow, etc...
Good Luck