Fill the paint well with white paint.
Turn on the air and grasp the airbrush as you would a pen, with your index finger hovering over the trigger. Make the motion to draw a cloud and press the trigger gently, mid motion to release the paint.
Use the white paint to draw out large, completely white cloud shapes. Airbrush the clouds in a circular motion until you have all the white cloud bases complete.
Fill the paint well with a darker blue paint. Use this paint to add definition inside your clouds, using the same circular motions to create puffy looking clouds.
Repeat with a slightly darker shade of blue to complete your clouds.