Write an article based on this "Get any blue colored paper. Take one of your oil pastels for the shade of the cloud. Add white. Smudge the colors. Put on the white oil pastel strokes. Add the shade."
You can use this technique in drawing a realistic cloud. Choose light gray for the shade of the clouds.  The shades of the clouds are usually located at the bottom part of the clouds.  However, shades always depend on where the light source is coming from. Using white oil pastels make circular strokes of the medium to the colored paper. Use your thumb or index finger in smudging the colors.  Carefully wipe the colors with your finger, according to the shape of the cloud, to show the smudge effect. Repeat the same circular strokes that you have done earlier.  Only this time do not put too much pressure on the pastel strokes.  Do it enough to show the actual shape of the clouds. Add light and few strokes of lavender on the bottom areas to show the shade of the clouds.