Add water to the joint compound and mix it with a drill and mixer paddles. Add the water in small amounts until the joint compound is like thick paint.
Scoop up some joint compound on the wide edge of a trowel and apply it to the wall. Push the joint compound up the wall, holding the trowel at a 45 degree angle.
Come back over the wall surface with the trowel held flat. Draw it back in short strokes, from different directions, creating the desired texture of skip troweling.