Here are some sky photos to consider as painting subjects. What kind of edges do you see? Would you want to work on dry paper or wet? How many layers would it take to realize the range of values you see?
Choose one of these, or go outside and paint the sky, or invent a skyscape. find a range of strokes and washes that will be acceptable to you before you put paint to paper, so that you are not searching with your brush. The more you adjust and correct your statement, the less it will look like a natural sky.