>I would forgoe the priming. Don't know why
>you would need to do that.
I've been reading that in some of the advice articles I've found on the web, about painting popcorn ceilings. Something about using a primer is supposed to cut down on the droppings and reduce the paint absorbing by the popcorn ceiling. I really don't know for sure as I am a complete rookie home-improvement-repair person.
Spraying will mean covering the walls or dealing with the paint that gets on them, so I was thinking about rolling. I will check out what it costs to get a sprayer, and assess whether I can do that myself or will need to get a contractor for it.
As to the oil vs water issue, thanks for the points you made. Sounds like water-based is the way to go.