Prepare the surface to be textured by painting it with a good quality primer. Apply the primer with a paint roller.
Thin premixed drywall joint compound to the consistency of pancake batter using water as a thinner and an electric drill and mixing paddle to mix the water into the dry wall joint compound. Ensure that the drywall joint compound is not too thick or it will clog the nozzle of the sprayer. If it is too thin, it will be runny on the wall. Pour the joint compound into the hopper of the sprayer.
Spray the wall with the dry joint wall compound. Adjust the sprayer's nozzle so the joint compound splatters on the wall, and is between the size of a dime and a quarter. Consult the user's manual to determine how to adjust the nozzle, as the process will vary depending on the model of sprayer. Allow the drywall joint compound to dry until it is tacky--usually between 15 and 30 min. Drying times may vary due to temperature and humidity.
Gently "knock down" the tacky drywall compound with an 18-inch trowel held at a shallow angle to the dry wall. Take care not to spread the splatters, just knock down the peaks.
Dip a paintbrush into the drywall joint compound and flick it at any areas you missed with the sprayer. Knock down the peaks once the drywall becomes tacky (15 to 30 minutes).