As you can see, there are a lot of possibilities. I don't limit myself to just one way of painting or drawing things. Or to one subject for that matter. I like to be versatile. I can do horror illustrations as easy as beauty.
The technique I use to paint illustrations has a lot to do with the time and budget available for them.
As you can imagine maybe, a full color illustration without outlines does take much more time than one that has a basic outline to it. Even the way the lines are made (wide lines or narrow ones) has an impact on the speed with which the illustration can be made.
Nevertheless, they can all be created swiftly enough.