The Roof Cleaning Institute Of America Training & Certification Forum
"Find A Certified Roof Cleaner Directory"

This is a link to a Slate Roof Forum started and run by Joe Jenkins.
It answers about everything you would want to know about slate roofing.
I have a few posts on the slate roof forum about the cleaning of slate roofs.
Lots of veteran slate roofers on that forum, perhaps a good chance for some of you guys to network with slate roofers in your areas ?