Cover the floor with 6 mm plastic sheeting. Secure the plastic to the bottom of the walls with wide masking tape. Lay cardboard on top of the plastic sheeting to prevent slips.
Cover the walls with the 6 mm plastic sheeting. Secure plastic to places where the walls and ceiling meet, using wide masking tape. Make sure the tape has good adherence so that it doesn't fall while you're spraying.
Rent a portable electric texture sprayer from a home improvement or construction rental facility. Put on a plastic body suit, goggles, dust mask, rubber boots, ear plugs and plastic gloves.
Mix white texture compound with water before you add it to the popcorn texture, following the compound's directions. Add 2 cups of popcorn texture to every gallon of water. Make a thin mixture. Put the mixture into your texture sprayer as instructed by the rental facility.
Spray a thin layer over the entire ceiling. Coat the ceiling with a second thin layer. Work quickly, and do not concentrate the spray in any one area. Use a ladder if you have high ceilings. Scrape off the texture with a putty knife if you mess up, and then respray. Let the popcorn ceiling harden.