I sent your question to Bill and here is his response:

The answer to the question is yes. These people in my stories are real to me. They have their own personalities, their own strengthens and weakness. I have also been a “student” of human nature most of my life. I have watched people, talked to them, shared experiences with them and had experiences of my own. It takes a good imagination to create a world. It also takes an understanding of people and how they work to create characters that are real and can interact with each other and their world. I share your (Jyssica) practice, if you will, of writing by thinking of the characters and their situation while I am not at my keyboard. I can’t tell you if I do it in my sleep, but my subconscious is constantly at work. But it is not of process of telling the characters what to do. Rather, it is finding out what they are going to do and why in the world I have put them in.

Everyone writes in a different way, her or his own way. There is no right or wrong way, only the way that works best of that particular writer. Some writers work with outlines. Some with diagrams. My method is all in my head. It works for me. Other methods work from others.