Simon
are you free next week? as i am running a course at the WDOAM at singleton starting Monday thru to Sunday where I teach the scribe rule (as partly described by Edward Shaw in Civil Architecture,1832?)One student has pulled out at the last minute so please phone the museum first thing Monday to see if anything is possible as regards joining the course.
The bottom line that no one has written a book yet describing how to scribe, but the texts mentioned by Ken are well worth reading as are articles in the M and T and some back issues of the Guild journal( e.g The cabadillo roof? again French scribe method).