It is possible to spray other materials with a lacquer spray gun besides the traditional lacquer and finish. The varnish is one product that is compatible with it and can be used in a lacquer spray gun. In fact, spraying varnish in a lacquer spray gun often gives a better result than other traditional applying methods. Spraying varnish on your wooden door will produce a smooth, blemish-free finish if you do it right. If your spray gun is compatible with thick materials, you will be able to use primers, enamels, and latex paints.