What is the purpose of lacquer or clear coat?
Vital for metallics and optional for solid colours, lacquer, or clear coat will add a clear film to the paint which can then be mirror polished. A superb way to seal race car decals and protect them, though it often attacks the decal and so must be used carefully.
It gives a hard shine similar to enamel and so may be undesirable for some finishes, but is a good way of polishing a model for the inexperienced, as the lacquer can be cut back to a shine and still give warning before you polish too much off! i.e. As soon as you see colour on the cloth, STOP!!!
It should be left for at least a week to ‘gas off’ before polishing otherwise your new shiny surface will dull again as the lacquer continues to shrink!