I would skim coat the entire surface and touch up any rough spots after that, prime and paint. If you lack experience/confidence, hire a pro finisher to do the skim coating. You already have done the grunt work. I hope you had the "popcorn" tested for asbestos, typically on 70's and older homes. If suspect, sounds like you have remaining dusts so be careful.

Here is a link that might be useful: popcorn ceilings-asbestos

Yes you can sand the rough spots. Yes you can use a small electric sander, but be prepared for a dusty mess around your head. I would actually try a pole sander first and see how that goes before breaking out the electric sander. The perimeter where the tape is you will want to skim over with lightweight joint compound like Sheetrock Plus 3 using a 4" taping knife. I would only skim coat the entire ceiling if you really think it needs it...if you can just sand some rough spots and the whole ceiling is smooth and even then you should be good to paint. Yes, SW primer is fine. Most of the dust should fall down due to gravity when you pole sand, but if you notice that there is still a good amount of dust remaining on the ceiling, then use a Swiffer or a dry mop before priming.

Great! Thanks for the advice. I don't think much of anything will show because we don't get much sunlight in this house. Bad lighting helps hide things sometimes which will work to my advantage on this issue. I will touch things up by sanding by hand and see if that won't fix most of it. I just want to make sure the paint sticks so I am going to dust some too before I try priming. I am just relieved that the popcorn is off and I can think about painting at last.
Thanks again.

Funny how the "A" word goes ignored. I ignored it as a youth pulling off what we later found out to be asbestos insulation off water lines at a plant where I worked. We wore paper masks when we wanted to. Am I contaminated? Who knows. Not noticable so far but asbestos dusts aren't something you want lingering around the inside of your house.

sierra, the "L" word as in lead gets ignored a lot too. Asbestos shingles and lead paint are so common in older homes. Many people think older is like 100 years or more and it's really only been since '77 or '78 since lead paint was banned (I believe) I'm too young to remember. :~D

That means houses that are only 30-32 years old could be wearing old coats of lead paint all over or in one place or another like doors, trim, etc.

Just better to be safe than sorry. Testing in most areas is relatively inexpensive or even no charge. Who knows what products that we are using these days will prove to be hazardous in the future, although with technology these days comes better testing and safety minded materials, so a lot better than the old days,(that i do remember cause I'm an ol' fart)!