A simple answer to a complex question! Solvents are, in fact, not the best solvent for acrylic paints. Acrylics tend to dry faster with the use of solvents. A better alternative is water which helps prevent lap marks from drying and produces hard, smooth, and shiny surfaces on your miniature projects. But when it comes to airbrushing - using an airbrush provides control over paint flow rates but applying thinned paint through an airbrush requires different methods than just thinning with water alone. The thinner you apply the paint, the less the surface tension resulting in a bigger spray pattern, thus affecting your ability to produce fine details in small areas or near edges.