I want to talk a bit about working non-destructively. Some rendering artists prefer to work completely non-destructively or never apply color correction directly to a layer. I began my career painting traditionally, with physical paint, markers, and color pencils. Where, every stroke the artist added to a matte was for real and couldn't be taken back unless you painted over it. In some ways, I think artists have lost something. Especially in spontaneity and directness, when you never have to make a final decision on any element.
Working entirely non destructively also results in huge file sizes. And projects with so many layers it gets nearly impossible to tell what layer is doing what, or find any element. This is counter to where the industry is moving, but I will often work directly on simple layers for the sake of keeping my project more manageable. Like I said, this is a matter of workflow, and you may want to work completely non-destructively in your rendering.