the application of paint causes the popcorn to fall, the primer phase will require two different coats and each coating will cause popcorn to fall whether primed or not. Its the rubbing motion of the roller that causes it to fall.
Under NORMAL situations when the first popcorn was applied, it was then painted and the paint acts like a bonding agent to keep the stuff affixed. some contractors do not paint popcorn because it has glitter in it. Then its up there on its own, when you then paint that with a roller it really comes down. sometimes I have seen this.
Now, you can buy a waggner spray gun for about $60 that will do the job for you. You will need to buy one accessory, its that bendable spray tube. This will allow the spray canister to remail level and the spray tip to be bent to aim at the surface. The product also comes with a long poly tube that you can fix into a gallon can, carry that can in one hand and sprayer in the other and wipe out that ceiling in one hour. The corners are easy also, spray only about 6 inches away from the wall ceiling intersections and then with a brush cut in the corners and sides. Will not take the actions you eluded to at all. The sprayer field can be controled by how close the head is to the surface. If your concerned, blue tape the sides and corners or buy a shild to protect that area.