The mineral spirits wouldn't do that, so it's the paint, try thinning it more. Get it close to water just to see if your bubble problem goes away. It shouldn't run as long as you run over it lightly after first application, and don't get caught up in trying to coat the area with the new color on the 1st, 2nd or 3rd application. It's easy to lay the 1st coat on too thick because you want to change the color of whatever you're painting, but really your goal should be just getting a smooth thin layer of the mixture on.