is to actually water down the compound to a much thinner solution then either roll it on with a very heavy knap roller or trowel it on.
If you roll it on, this is only the vehicle to get the compound on the wall, then you skim it or trowel it smooth. this takes about two to three passes. I would recommend using a fast drying compound like 20 minute mud. It will dry must slower than this because you'r watering it down.