While you can do skip trowel texture work with a simple joint compound, it actually tends to work a lot better if you've diluted the compound before you use it. The reason behind this type of dilution is that when you have a joint compound that is less consistent than average, it is easier to work with in terms of shaping. Since shaping the wall or ceiling is really the end goal of using a skip trowel texture method, diluted joint compound is a very good thing to have.

The dilution of the compound can be carried out with water. Depending on the size of the area you'd like to texture you can take a small bucket and add the compound and water before mixing it or you can just take an entire bucket of the compound and mix a couple of cups of water in. You don't want the mixture to be too runny (especially if you're doing a ceiling), but you do want it to be workable.

Once you have your compound and water formula, you can begin to apply it to the walls and ceilings that you need to work on. At this point you don't need to worry too much about how it gets onto the surfaces, so long as it gets there. A paint roller is an acceptable way to get this done and certainly a practical one if the surfaces you need to cover are quite large.

When the compound has been applied to the target surface, use a trowel to smooth it down with a stroke to one side. Bring the trowel back with a stroke to the other side, alternating between a smoothing motion and a slanted position where the edge of the trowel disturbs the smooth texture you've just created. Alternate at random intervals until you are satisfied with the look and then wait for it to dry, cleaning up any excess material either on the surface or fallen to the ground as it appears.