i put my seedlings into the biggest rockwool i could find( i think they're 6'' cubes) about 3 days after i got them. They were probably only one or two weeks old at the time. (about 1.5'' - 2" tall) Then i put that in a bucket with hydrotron all around it and covering the rock wool. The rock wool is pretty absorbant, but the hydrotron isn't very absorbant, i think it just helps keeps things moist and helps prevent the top portion of the rockwool/roots from drying out. i have mine on a continuous drip system that runs all day and shuts off at night.

as far a nutes go, i just used gen hydroponics "flora nova grow".
it has recipies for seedlings, early growth, mid growth, late growth.
just follow instructions on bottle. It's about 1/4 tsp. per gallon for seedlings. I just used that and watered the rockwool with it and put it all in a pie pan. then just checked everyday or so and felt the rock wool. when the nutes in the pie pan were all sucked up and dry i just watered a little more. just always make sure it's moist, but not soaking wet. I kept them like that for about 3-4 days, then put it all into the power grower buckets with the hydrotron.

im definatley a newbie, but this has worked good for me so far.i hope this helps some what.

here is my set up/grow log....
http://boards.cannabis.com/hydroponi...fl-system.html