I just read Robert Boice's "Professor as Writers: A self-hep guide to productive writing." I have to admit, I am a bit embarrassed that I did not find it during past literature reviews for my own work. It is a 1990 book, and is a wonderful, systematic approach to writing productivity that is based-upon the author's (and other scholars) research. Readable, and outstanding in all ways. A bit dated in terms of technology, but an important book.
I have to admit it, I think in many ways it is better than my book, Practical Tips. Something to which to aspire! I think they actually complement it other well.