What a shame, LL tagged

No, but I did some research on what was available and works, and both BC Parks and the Little Smoke Bluffs committee are OK with it. I've tried several things, including some spray-on stuff called Goof Off, essentially a solvent. The stuff I use now is called Removall - "Industrial Paint Stripper for Concrete and Masonry". In the fine print it says "biodegradable", but I'm not sure that I believe it. Anyway, it's a paste that you goop on. Let it sit for a while, then scrub and rinse, scrub and rinse, then re-apply. Usually I use a soft brush, sometimes with a bit of help from a wire brush. For areas that were lichen and moss free, the result isn't very visible. Otherwise, the graffiti is gone, but you end up with a visible cleaned area, which may take several years to fade and grow over. As you can see from the following, from the Apron three years ago.

Sep 3, 2012 - 01:37am PT
The magic stuff is called Removall. It was originally made in Vancouver, but maybe is now made elsewhere? There may be two or three varieties. It comes in a plastic bucket, much like an ice cream tub - four litres for about $45, which is enough to do a lot. (It's allegedly biodegradable, too.)

Anyway, you need Removall, a good stiff scrub brush, lots of water, and incidental things such as work clothes, something to protect your eyes, lunch, something to read, etc. Removall is a cheerful orange paste. The system:
1. Daub it on the painted area. (It sticks quite well, and I just use the scrub brush.)
2. Wait patiently at least 30 minutes, better still more. Until it seems to have entirely dried up and disappeared.
3. Rinse and scrub like mad, rinse some more. Lots of water needed - I carried 15 litres to the top of the Chief today, to get the one that was up high, unusually so. Plus serious elbow grease.
4. Reapply, and repeat steps 2 and 3.

Two to three applications usually do it. Each pass takes 80 - 90% of what's there, so at the end there's 1 - 2%, usually in crevices and niches. That's a realistic goal.