requires water to break down the popcorn and make the job much easier and not dusty at all, but the wet caked accoustic is a mess.
here is what I do. remove everything in that room, plastic the walls, plastic the floor and have a friend remove the fallen stuff as you concentrate on the removal
I get a deck sprayer and use the fan tip and spray that popcorn until it turns dark gray. I reapply water again as I go. You do not want to over saturate the surface but you want it to soak into the stuff. Now with a long handled scraper, I use the vinyl tile scraper blade. I can stand on the floor and remove the stuff without being on a ladder and crooking your neck and back.
This is the key part, you need to set that blade at about a 60 degree angle and actually shave off that stuff. It is wet enough, it will come off like shaving your face, or legs. Do not gouge the skin of the drywall, if you do just patch it.
This is easy and fast and still a mess, but nothing airborne. Now, before you paint or whatever. let this dry for a good three to four days. Then prime and paint or whatever.