No, more paint or primer is not going to fill in the depressions....remember gravity is a factor here too,,,which I guess might explain the previous stalactites. Kind of scratching my head on that, I must admit.

I would skim the whole ceiling with joint compound, personally. I recently did that in a room with heavy orange peel texture on the walls. I bought a sander attachment that hooked onto my shop vac and found that it worked surprisingly well to minimize dust.

I also tried one of those sponges for " wet sanding" joint compound....I didn't care for that as much, but it might be acceptable on a ceiling.

Are you using flat paint on the ceiling? How big a space is it?

Yep, using flat paint.
The kitchen has an irregular shape, but about 600 sq.ft. The practice foyer also has an irregular shape and about 150 sq. ft.

What is the sanding attachment you used? I've used the one that has a fiberglass mesh attached to a flat base. Worked ok, but it's hard for me to use.

Yes, the flat attachment uses the mesh sheets...its not the most comfortable or quickest thing to use, mostly because the shop vac hose is not as flexible as I would like.... but anything to cut down on that horrible dust! The one I got was a hand sander attatchment, but thought they also made one for using on a pole...not sure.

Do you have one of those super wide rollers? I love those for painting ceilings too.

Here is the pole sanding attachment, which looks like it gets pretty good reviews.

Here is a link that might be useful: pole sander attachment

coll_123,
Thanks for the sanding info.
I just finished skim-coating the ceiling in the foyer. Tough job: the pock marks made bubbles in the joint compound. So the job is really bad.
I'll dig up the mesh sander and see if I'm stronger now (unlikely).

It shouldn't take strength, but it can be awkward, using that thing, maneuvering the hose.. I hope your bubbles level out.

One other thing- I'm not familiar with adding extenders to paint ( I do for decorative finishes but not flat paint). I wonder if that could contribute to you stalactite formation, because the paint is not setting up fast enough and therefore wants to drip downwards, . I really would recommend the extra long roller, and not too long a nap. I would say a 3/8 ......maaaaaybe a 1/2" . I'd go with the 3/8 extra long roller, if you have a smooth surface now. Good luck!