How do I paint over a textured ceiling without removing the texture?
Priming then painting: The texture is water based, so you need to prime first with oil or shellac based primer.  This will seal the texture and &quot;waterproof&quot; it.
Use plenty of ventilation and possibly an organic respirator.
Once primed, any paint can be used (make sure the full drying interval is used).
Removing: will work before any painting.  Put down waterproof tarp, wall-to-wall and taped 6&quot; up.  Use a misting  hand sprayer or a garden sprayer.  Let soak 15 min, respraying  if dry spots develop.  Scrape with a long handled pole and a stiff angled putty knife.  Keep the knife flat and start slowly until you get a rhythm.  No sense in making another repair for gouges.  Clean any residue with a new sponge mop and some TSP or a light detergent.