CLOUDS
various types of clouds exist; the colors and shapes depend on many factors moisture content, sunlight, other clouds, elevation and wind to name a few. I am sure a meterologist can provide a more exact science for them. However, being an observer by nature (sounds creepy) and as I reviewed an old Model Railroader article on clouds I came to realize that my impression of clouds came from cartoons and paintings and not necessarily from reality.
The article said to observe clouds, so I did. The clouds I was looking for were particular; being clouds nicely defined by a vivid blue sky. The ones used in the MR article. The observation revealed that clouds are sharp and defined at the tops and gradually become more difused at the bottoms. WHY? Because as our sun hits the atmosphere the higher cload forms get more direct light while the lower parts of clouds get light filtered thru other clouds so they tend to be more difuse.
Also, clouds at the horizon tend to be vary difused because we are looking many layers of clouds that circle the planet at that point. SO how to model the clouds as observed. The MR author used stencils of actual cloud forms. How? He taped light colored thin posterboard on his windows and traced the cloud shapes he saw thru the board on the board.
Next he cut out the shapes and had a stencil. He did this a few times with different clouds to get a few unique stencils. Now after painting the wall a specific shade of blue, he held one of the stencils up to the wall close to the wall and with a spray can of white paint painted the top of his cloud.
For a larger wall he used many stencils and parts of stencils to cover his wall with the TOPS of clouds. Next he went back to his first set of TOPS and moving another stencil a bit away from the wall he sprayed the diffused part of the cloud BOTTOMS. Using multiple stencils across the wall to create unique clouds.
THERE IS ONLY ONE WAY TO DO CLOUDS . . .the way you feel most comfortable about. This is mine.