Vallejo Model Color needs real thinning — start around 1:1 paint to Vallejo airbrush thinner and adjust until the mix runs like skim milk off a stir stick. Vallejo Model Air is pre-thinned for airbrushing and usually sprays with just a few drops of thinner or flow improver at 18–20 PSI.
Thin with the brand’s own thinner or a quality acrylic thinner rather than water alone: water weakens adhesion and dries chalky. A drop of flow improver in the cup also slows tip dry on long sessions.
Go deeper in our paints & primers guides.