| ''[This I got from my buddy, a Pittsburgh Paints Regional Manager, earlier this year]''
Hummmmm! Somebody that works for a major paint company recommends using a major brand? The first 10 years I was out of school I worked a a chemist at a paint company. I was more into automotive and industrial finishes rather than house paint. Still I do know some things in addition to my personal experience.
Several years ago anticipating a move, my wife and I did a bunch of painting. We started with some Sears stuff she bought. The ceiling took 2 coats and avoiding lap marks was tough. Going on to some other rooms, I decided to slap on cheap stuff from Big Lots on. One heavy coat did fine and much easier to work with. We didn't move and years later it looks better than the Sears stuff.
Look at the label. Go with the highest percentage of titanium dioxide or TiO2 you find. In a white or pastel, that usually is the biggest factor in how well it covers. If the label doesn't give the composition, go with a brand with less to hide.
I used a vapor barrier paint on some of my ceilings I thought came from Sherwin William's, but it could have been Benjamin Moore. It appeared to be a pigmented shellac. I left it exposed on the ceiling as a flat white. Did a couple of bathroom ceilings recently and wanted semi gloss. I thought if I had to put another coat on it, I would just use shellac. I could buy a small can of it, and it goes bad if not use up soon. Semi gloss latex doesn't spread right over shellac. I am not sure it sticks right either, but at least ceilings get very little wear and tear. | 
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