Tough As Nails
Anti-Grafitti Tests
  The Marker Test
  a Sharpie Sharpie marking on a sign Sharpie removed with isoprophyl alcohol  
The Spraypaint Test
  a can of aerosol spray paint over-the-counter grafitti removal spray spray the remover all over the affected areas let is soak for about 5 minutes
a stiff nylon brush is perfect for this job work the remover solution with the brush almost done for the last remaining residue use lacquer thinner
use a wooden or plastic scraper to get some of the stubborn parts as good as new!