Spread newspaper around the area you will be painting to protect it from overspray.
Remove the drawers from the dresser and set them on more newspapers with their faces pointing upward so you can paint the face and the exposed edges of the faceplate. Remove the drawer pulls by unscrewing them from the inside of the drawer with a screwdriver.
Place a fresh sheet of sandpaper in your power sander and sand lightly over the entire surface of the dresser to remove loose paint and provide a roughened surface for the spray paint to adhere to.
Dip a rag in water and squeeze out as much water as possible so it is just barely damp. Use this to wipe all sanding dust off the dresser. Wipe the dresser again with a dry rag to remove any remaining moisture.
Shake your can of spray paint for a full minute before applying, then spray it according to the directions on the can, which usually indicate using a sweeping motion 8 to 12 inches from the object's surface. Apply paint to all surfaces of the dresser that will be visible, including drawer faces and edges.
Apply a second coat if necessary after the first has dried, which may only take about 15 to 30 minutes. Replace the drawer pulls and reassemble the dresser when it is fully dry.