I have a new favorite primer, Tamiya surface white primer. I read about it in one of the RESS forum posts, sorry I don't remember who posted it. It is made for miniature painters and is incredibly fine. And it comes in white, which is ideal for my pastel application.
I've only used it on about 8 minis so far and haven't even finished the first can (I bought several), but it goes on fine and thin. No loss of detail on those tiny wrinkles and veins. And it dries nicely to a slightly chalky feel, which makes me believe it will take pigment well. Haven't yet started painting, but I don't foresee any problems.
Not sure yet how it will fair on plastics. Tiffany Purdy told me there was some chemical (aluminum something???) in white primers that interacts with the plastics, which is why so many of them stay tacky after priming. I thought it was just the Krylon formula for their sandable primers, but maybe it is all white primers? I rarely, rarely work in plastics, so I haven't done alot of exploring on the topic. If anyone has any advice/thoughts on priming plastics, feel free to let us know in the comments! And since these cans are written in Chinese characters (or maybe it's Japanese?), I wouldn't be able to read the ingredients if I tried!
Anyway, I think this is a wonderful addition to the prepping aresenal. A must have for prepping minis scale models, in particular. I don't believe it is carried in any hobby stores, but it can't hurt to look. I ordered mine over the internet (the link above will take you to their site - it's the cheapest I'v found so far, let me know if you find it elsewhere for less).
Note: always protect yourself when working with spray primers and paints by wearing a gas mask and only spray where there is good circulation! Even the outgassing while they dry is better done away from people and pets.