This is a process of painting anime style cumulus that I learned from all the books I purchased. During the time this tutorial was written, I am still not that good with clouds painting, but hopefully this will be useful for you.
ArtworkHere are some of my artwork with cumulus cloud paint with similar method.
ReferenceDeviantArt Anime Cumulus Cloud Tutorial
DeviantArt Long Road
DeviantArt Pylon and Cloud