Here's how I see it working, once tag wikis offer better guidance:
paint should be used when the question is about dealing with paint in a generic way, and not specifically about one type of paint or another, or when the type of paint isn't known. Examples:
painting should be used when asking general questions about the act or process of painting itself (verb form), to specify materials are going to be used for a painting project or existing painting. Or, when the question is about an existing painting (noun form).
painting should also be used with specific media tags, if the the question is about the process of painting with that medium, just as you would use drawing + pencils or drawing + charcoal.
Specific tags, such as watercoloring, oil-paint and acrylics should be used when the question is specifically about working with those materials, as the methods of applying, preserving, mixing, etc. are unique to those mediums. They don't need to be used with other tags, as seen here: