"The writer faces the writing process fearless, not knowing where the writing will take them..." (BPR ch.11) Coming from the perspective of a Language Arts teacher this is very true. I encourage my students to dive in, especially on a creative piece, and let the words lead them. I discourage outlines and other forms of pre-writing that box them in. Sometimes it is okay to not know how your story will end. I agree as well that teachers should be writers. How can I teach something if I don't model or practice it in class?
My success as a writer only came from practicing. You cannot pick up a book, read about writing then magically write. Just like a musical instrument, it takes practice. My students write daily, and even if writing was not my content area I would still find a way to practice that skill.