A little of this...
I use a mix of flow aid and extender with my Adikolor paints. I put just a little paint on the pallette, and then add as little of my mix as I can. I mix it in until it\'s evenly spread in the paint, and see if the paint is the consistency that I want it.
Sometimes I add more, but that, as Chrispy said, is where practice and experimentation comes in. The way I do it, I have *about* 4 times as long before the paint starts skinning on me, but I always have to be careful not to dilute it too much or the paint loses it\'s ability to cover the primer.