Technical Contrast Medium

Thins contrast paint to a consistency that becomes smooth without losing much pigmentation, unlike thinning with water.
Can be used to thin and blend contrast paints on a model after they have been applied, kind of like wet blending, but with less control.

Also physically smooths contrast paint over an already smooth base/ primer. It can't save your finish if the base or primer is "bitty" or textured.

This medium can also be used to thin normal acrylic paint without losing much pigmentation. It can't "contrast" a layer or base paint, but it can thin them evenly for basic glazing or rudimentary washes.