Yes, the rockwool works very well. I start clones in 1" blocks then transplant them to 3" blocks once they've sprouted good roots. I condition the rock wool by soaking it for 24-48 hours in a mild nutrient solution (see chart below) before putting in the cutting or transplanting to the 3" cube.
When inserting them into the buckets with hydroton I first fill up the buckets to the lower of the two flanges around the outside top of the inner buckets. Then I turn on the system and make sure the flood level is
just below the level of the hydroton. This allows the roots to drop from the block to seek the water but does not soak the hydroton with every feeding. This is important because a constantly soggy block of rockwool at the base of the stalk is not good.
Once I've got the hydroton level just above the filled water line, it's super easy to simply set the blocks on the hydroton and using an old pitcher (or a hand scoop) pour in more hydroton around the block. Once I cover the block it's done. Way easy and the plants have a stable root ball to work from. Hardly any shock at all. Takes a few days for them to drop the roots and start uptaking nutrients, so I usually bottom-water the rockwool block before placing them in the system (I use an inverted Frisbee to hold a bit of R/O water and dip the block into it for a few seconds, allowing the water to wick up into the rockwool).
Here's the rockwool soak (and feeding schedule) I utilize:
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