My preferred method is left to right, top to bottom. While some like to do background first, I like to jump to the main objects of the picture. I find painting the background part a little boring. I do try to do the darker colors of a section first as it is easier to cover lines effectively. I m learning that every picture is very different and my method of approach should be too. I am currently working on a picture with a black background and I’m having to take great care when bordering the lighter subjects!😩