I used your product, Elephant Snot® to remove the graffiti. For the benefit of others that wonder if this stuff really works, I'll explain the process that I went through.
The day was about 48-51 degrees and we had intermittent rain/sleet. The graffiti had to be removed that day as the City of Morgantown had given the property owners a time line in which they expected the graffiti to be gone...this was the last day as it took a while for me to decide on a product to try.
I brushed the "Snot" on with a wallpaper brush and let it sit for about 45 minutes. I then began power-washing it off at about 1400-1600 psi cold water. Much to my surprise, virtually all of the paint and marker simply ran off with the water! Surprisingly, a small amount of the white and a bit of the red needed a second application which I did as I was washing off the rest. It all came off. I should mention that although I purchased a 5 gallon bucket, all of this was finished with less than 2 gallons.
Just for reference, the graffiti in the first picture, "burning" was about 1 year old. The remainder of the graffiti was no less that 23-24 years old and had resisted attempts to clean it with acid washes. After the "Snot", there was absolutely no damage to the brick or the mortar.