Oh man, I know how you feel.
My battle is with graffiti. I have tons of cheap brushes and various masonry paint. Our bridges and bike paths get tagged constantly, and the next day I paint over it.
I have a "war" going with a couple graffiti artists. I paint over it and they tag it. Since I went out one day and painted the entire bike path bridge, my paint matches perfectly, so when I have to cover graffiti there isn't that ugly miscolored rectangle you usually see.
But they come back.
I know it's school-aged kids because it never happens on school nights, only in the summer and on Friday's and Saturdays. Also, there's a kid who drives a golf cart (we are in a golf cart community) that has stickers all over his golf cart that often are the same as the graffiti, so I think I know who it might be.
The funny part is that these guys I'm in the graffiti war with think they are actually in some kind of contest they can win.
There's only one possible loser in this contest as I'll keep painting over their work, and they'll keep tagging.
The difference is that only one of us is going to get prosecuted as a result of his actions when he gets caught.
I can't wait to catch them. In our town they'll get nailed. I was just talking to a cop the other day and they've had a kid locked up in Juvenile Hall for three months for repeated graffiti attacks.