thin it until you can place the stir stick against the side of the paint bottle and it just leaves color on the side of the bottle as it runs down,,,,,,,,if it "runs slow" and leaves a lot behind,,,,,it is too thick,,,,,if it runs fast and seems to want to come off of the bottle side,,,,,it is too thin
thin Italeri, Vallejo and Color of Eagles with the same thinner,,,,,,,,,use the newest Vallejo thinner,,,,or follow this guy's lead,,,,,,,,there are other linked pages attached to his main article
www.rebelscale.com/.../painting1.html