This was the room devoted to whenever cover artwork needed to be made somewhat more fancy by using an airbrush. These guys made much more money and had to be pretty good with air-brushing. The trick here was these guys too, followed the same process outlined in the text above. But they did it with thinned opaquing medium to get a “faded edge” or a “tone change” over an area. If there was a purple sunset-ish sky, they made the graduated change that would be printed in two colors, red and blue, to get the desired purple. Pretty tricky stuff! And it could get real complicated.