Cover all walls and floors with plastic sheeting and masking tape to avoid getting texture material on any other surfaces.
Mix the texture material, or drywall mud, in a 5-gallon bucket, according to the instructions on the bag. The mixture ratio will depend on the type of texture being applied.
Connect the air compressor hose to the gun and turn on the air compressor.
Add texture material to the hopper of the gun. It is best to start with a small amount at first.
Holding the gun 1 foot to 2 feet from the ceiling, pull the trigger to spray the texture material on the ceiling. Use slow, smooth movements to keep the texture material as even as possible.
Add more texture material to the hopper as necessary, checking the consistency and stirring when needed.