Before, when I was still starting to paint, clouds was one of the hardest sugject I painted. My clouds before was like big huge gray rocks with constant same curve shapes. I was really struggling. And in this topic, I hope I can help you lessen the struggles and help you improve painting clouds. I also have old videos that I will include here.
How to Paint Afternoon Clouds
Proper Way on Painting Clouds
How to Paint Clouds (Old Video)
How to Paint Afternoon Sky and Clouds