Measure premixed joint compound into a mixing container such as a 5-gallon bucket. Add water according to package directions for ceiling application. Write down how much compound and water you use so you can match the consistency in later batches. Mix the joint compound and water well with a mixing paddle attachment on a drill.
Hold the trowel in your dominant hand and the hawk in your other hand.
Place enough joint compound on the hawk so you can easily hold the weight. Pull a small amount of compound off the hawk and onto the trowel. Smooth that compound over a section of the ceiling. Create the pattern you practiced making. Cover the entire section of the ceiling with mud.
Clean the bottom and edges of the trowel on the hawk. Lightly run the trowel over the mud on this section of ceiling once it is semi-dry to knock off any sharp points and to create a smoother finish. Omit this step, if you prefer.
Repeat loading the trowel and applying mud to the next section of the ceiling. Continue this process until you cover the entire ceiling. Add more mud to the hawk, as needed. Periodically wipe the joint compound off the trowel and back onto the hawk to help keep the pattern looking the same.