Just! Thinning is an important tool when applying car paint or varnish. Diluting the paint with thinner makes it thinner and more fluid, making it easier to apply to the surface. It is important to choose the right type of thinning to achieve the desired result. There are different types of thinner, such as cellulose thinner and acrylic thinner, and the choice depends on the type of paint or varnish used.