Today I am cleaning a metal roof in WA state . There is heavy lichen/algae on top . Prior to this I’ve always used a ****taI’ll of green wash and oxi wash with SH at 3-4% and follow with final wash and rinse . This roof isn’t walkable but my question is if you guys would brush the whole roof or allow the solution to do it’s work and weather off naturally ? The two panels on the right were scrubbed with a medium bristle brush and it took some elbow grease .