realisitic cars

So I saw in Micro Mark that they sell a rust paint that's water base and claims to give realistic effects. Wow where they right. It is called Model WASH for the rust effects. It made by vallerjo. Here's a pic of the bottle and trailer I rusted out. I decided idea to use an older 45'...

So while doing some weathing (IDK if thats correct type but oh well) I was looking at some images. I saw a bunch of graffiti on cars. That triggered and idea to make them look even more realistic. As I started looking at graffiti on rail cars it occured to me that people tag buildings as well...