Two things to add here:
Rockwool should be preconditioned before use by soaking it in water and ph adjusting the soaking solution to about 6.5 before use. Rockwool as purchased has an elevated pH. It is not ideal. Shake the cubes out afterwards to get excess water off.
The other thing is that if you're going to dip the shoots in anything immediately after cut, the best solution imvho is actually dip n grow diluted to about half the strength it recommends on the bottle, and leaving the cut in it for a few minutes. It absorbs well and has fungicidal properties.
I've never had comparable results with gels. And if you pre soak in water and then go to a gel, you are kind of shooting yourself in the foot in terms of absorption. An already-wet sponge doesn't hold much soap