Choose a sky background color
Paint the sky first and let it dry
Mix white with a little blue, gray, or pink for cloud tones
Use a soft, dry brush or sponge
Dab in the cloud shapes lightly
Build clouds in layers from light to dark
Keep cloud edges soft and uneven
Add darker tones underneath for depth
Leave some areas of the sky visible
Blend gently where needed
Vary cloud size and shape
Add highlights with pure white
Refine edges sparingly
Let each layer dry before adding more detail