The benzalkonium chlorides definitely killed the lichen. But it did take a mild scrubbing with a brush to remove the corpses. Please note that previous scrubbing with the same brush and bleach had no effect on the spots. I apologize that I used a washer for the sizing comparison - I didn't have a dime in my pocket. The washer is a little bigger than a dime and a little smaller than a nickle.
I also applied the 5% benzalkonium chloride solution to a portion of our dodger canvas. Please note that this canvas is more than 10 years old, and has lost most of its water repellant qualities.