Remove wall hangings from the room and set them outside, along with smaller pieces of furniture. Push heavier pieces that you cannot move outside near the center of the room and cover with drop cloths. Spread tarps or plastic sheets on the floor to catch drips. Secure plastic sheets over the walls of the room using tape.
Position a stepladder firmly on the floor at a corner. Hold a trowel with a beveled edge in one hand and apply an even amount of Spackle over its blade. Glide the plastered end of the trowel over the surface of the ceiling to cover a few feet.
Make your desired design on the plaster using a putty knife. You can press the edge of the knife flat against the Spackle and move it around to create peaks or swirls. Alternatively, insert the tip of the putty knife in the Spackle and move it along the covered area to create random lines. Another way of decorating a ceiling is to insert the teeth of a comb into the Spackle and extend it along the surface to create fine lines or ridges.
Spread more Spackle over the ceiling and repeat the process of making decorative designs over it until the surface is completely covered. Review the Spackle on the ceiling after you apply it every few feet to access it for consistency. Leave the Spackle to dry for one day.
Inspect the Spackle before painting the ceiling. Leave the plaster to dry for another day if it feels cool or moist. Paint over the Spackle using a roller with a heavy nap. Apply little pressure to the roller as you move it horizontally and vertically across the ceiling.