Lacquer is one of the oldest finishing materials there is, dating perhaps to the Egyptians. Asian craftsmen used the sap of trees or insect bodies dissolved in a solvent, but modern lacquer is made by dissolving cellulose in nitric acid. Lacquer hardens when the solvent evaporates, which can happen quite quickly. Good spraying technique involves holding the gun close enough to the work surface that the lacquer doesn't turn to a powder in the air, without holding it so close that the finish runs or separates.
Pour lacquer into the cup of a siphon gun until the cup is about three-quarters full and screw the cup on. Connect the air hose and turn on the compressor.
Point the gun at a test surface and test the spray pattern. Adjust the air pressure and the tip of the gun until you get a pattern that is about 6 inches wide at a distance of 6 inches from the gun. Rotate the spray tip to make the pattern fan out in a vertical or horizontal pattern as desired. Add thinner to the lacquer if the spray is weak or chunky.
Hold the gun about 6 inches from the work surface and spray in a smooth up-and-down or back-and-forth motion, overlapping about half the width of the spray pattern on each pass. The goal is to achieve a shiny, wet coat without runs or dust.
Hold the gun farther from the surface or move it more quickly if the finish sags or separates. Finish separation may also be a result of wax or silicone on the surface you are spraying.
Hold the gun closer if the surface is dusty or bumpy. This happens when the lacquer dries before it hits the surface. If this is a persistent problem, the thinner may be too volatile. Try a different thinner.
Let the lacquer dry for about an hour. Sand it with fine sandpaper, wipe off the dust, and spray another coat. Continue in this way until you are satisfied with the finish.