For those peoples who have access to PS and want a create watercolor for character, but don't know what to do exactly. I desided to make dedicated topic (maybe it should be pinned), becose it's will be easier to find this information, rather than i simply post it in Portraits topic. Also becose i want to provide a detailed step-by-step guide, and this lead to huge size of posts.
This technique i'm using long enough, and it was used for my Enhanced Companions Portraits mod: https://www.nexusm