I've been thinning the paint (rustoleum premium) to about 40-50% with mineral spirits. I ring out the roller pretty thoroughly in the pan and then apply it by overlapping sections until it all looks flat and nice. No bubbles, I go slowly enough that they seem to pop right out on a second pass from the roller.

It just isn't what I would call a flat paint surface. The pics I've seen of other cars are so varied it's hard to tell what to make of the comparision.