I always use Vallejo primers on my miniatures. It is by far the best quality!

While the color and application is fine, after some unfortunate experiences, and trial and error to verify, I've found that certain varnishes (Rustoleum Ultracover in particular) does not work with the Vallejo rattlecan primer. It gives that result where the paint starts to almost wrinkle slightly, completely ruining the finish. I've controlled for temperature and humidity - which can also cause that - and am pretty sure it is just the paint+varnish. I have not had the issue with Testor's Dullcote though (which I used as a comparison for my tests). Not saying it is a terrible paint, and if you go in knowing what to use to protect the finished product, it works fine, but I ruined several paint jobs before I figured out the dang issue...