If you squeeze the rockwool you will destroy the use of rockwool. It is meant to be a medium that is airy and by squeezing it you remove a lot of air pockets.
The cloning method I use: Soak the rockwool in (pH 5.5 water with 1.5ml/L 29%H2O2 added.) for 24 hours. Then I gently shake out the...