Two very good points
1. scrub, scrub, scrub, scrub, scrub, have a rest. scrub, scrub, leave it & come back to it last. scrub, scrub, you may get lucky! that's for the real bad stuff. I've had a few that wouldn't come off at all & had to be scraped off. Normaly though a good scrub will sort it.
2. That sinario is a problem, public footpaths with your trip hazard all over it
you could put signs up & hope for the best, the job would REALY have to be worth it though.
Tony