We are completing a major overhaul of our small,urban yard, L-shaped back yard and have run our G-Scale train around the yard, including through a tunnel under the waterfall. The yard is enclosed by concrete block. I would like to paint (actually have someone who is an artist) one section of wall where the track runs close by, with a railroad town, some scenery in the background. What type of paint would be appropriate and last? We are in southern CA with lots of sun on that section of wall.