I never hand water. I let my clones get nice root growth before I put them into DWC. When I transplant into the net cups, I put the rapid rooters, rockwool or whatever on the bottom of the net pot and then keep the water level almost even with the bottom of the net cup. If you have good bubbles, the rockwool will stay hydrated enough so that it does not dry out. As the roots grow into the nute solution, I lower the water level.