We removed the popcorn using a damp technique, covering everything with painter's plastic to control the dust. After we remove it, we sand and dust ceilings well, making sure not to disturb the paper tape between the butt-joints. After sanding and dusting we spray double-knockdown on ceilings. After texture cures we seal the ceilings with an oil-based primer/sealer. Heavy clean-up. Then we repainted all walls, doors and trim.