wetting it does help to prevent the fibers from going airborn but you may also need to wear some sort of filter mask to prevent breathing it in if your cutting alot of it.
have ripped cubes into but they didnt look anything like a cube after done so not sure what you would use to cut it a knife might work.
it will dry out and be usable and retain its neutral ph have even heard of reusing rockwool from one grow to the next so you dont necasaraly have to replace it every grow.