I came across this article on Raymond Parker’s VeloWeb. The web address is http://veloweb.ca (he’s Canadian eh.) Very detailed and well photographed instructions there. While he is installing Honjo fenders, the guide will work as well for other metal fenders such as Gilles Berthoud and Tanaka.
Also, lo and behold, there is a Honjo Fenders group on flickr.com. Lots of good photos and ideas for mounting fenders there.