Stir together water and a small amount of laundry detergent-- just enough to create bubbles. Add the mixture to spray bottles or a water pumping device. Drench the popcorn ceiling. Allow the ceiling to sit for about 20 minutes. If it is still stiff, continue to add water until the ceiling is extremely moist.
Scrape the finish off with a trowel or metal drywall blade. The popcorn ceiling should easily come off of the ceiling. Continue the process until the entire popcorn ceiling is removed. The process is tedious and may be difficult in some areas.
Wash the entire ceiling several times to remove all remaining ceiling texture or visible drywall dust. Use a wet rag or sponge and clean water. Continue to wash the ceiling until no residue is left.
Spray the ceiling with orange peel texture. The product is available in spray cans for small ceilings, or use a spray gun for larger areas. Mix together joint compound thinned with water. Add to sprayer and apply to the ceiling. Smooth the texture with a drywall trowel. Allow to dry about 24 hours before painting.