Apply cling plastic sheeting to the cornice and walls. This type of sheeting is designed to stick to the wall surface snugly. Add a line of painter's tape along the edge of the cornice to provide a clean break. Cover all window, door openings and finally the floor with the cling sheet. Bag any chandeliers in plastic bags wrapped with tape.
Mix your texture product in a 5-gallon bucket with water and pour it into a texturing hopper. Connect the hopper up to an air compressor. This can be very loud so position the compressor outside a window and thread the hose inside. Wear a painting suit and face mask.
Spray the ceiling texture on the ceiling. Hold the hopper gun at a steady distance and apply the coating as thick or thin as you want. You may need a second helper to knock down the peaks of the texture using a wide drywall knife. Apply one coat of texture and allow it to dry for an hour. Return and fill in any gaps you may have missed.