Lacquer coats

After decaling you apply a matt clearcoat,  both to seal the decals and to create a uniform (flat) sheen.

I put three coats of lacquer over a flat finish yesterday and it still did not look like a smooth enough surface for decals. Also, if you apply lacquer in decal spots will there not be a different sheen to the model than if you had painted the whole model with lacquer?

Since lacquer dries quickly, I find I can do it in one "coat" where a coat means a session with the airbrush. I may make a couple of passes, waiting a few seconds between passes. I am usually doing several different spots for decals, so by the time I make a pass at each spot I can go back and make another pass at first area, and so on.

Kind of like asking how many holes it takes to fill the Albert hall...

Just enough to get a glossy surface when dry.