You may have noticed that boxcars and reefers often look like their roofs are unpainted. With the exception of some modern cars that use galvanized roofing materials, most have simply shed their paint over time. A number of years ago two talented gentlemen by the name of Greenberg and Nash invented a scheme for the simulation of peeling paint. They used common rubber cement as an initial coating with an airbrushed final color over the top the cured rubber. You then remove the rubber cement by rubbing the patches with an eraser or even your finger. This works well enough to have become a virtual standard technique in most modelers tool kit.
You can get a similar effect by using Floquil’s Silver lacquer paint to paint on the effect. You need to use a fine brush to define the edge of the peeled area. Visualize a rough and irregular surface caused by the paint flaking off. This is the image that you want to achieve. Once the Floquil has dried, you can soften the contrast of the basic roof color and the shiny metal look of the silver paint. You can do this with series of acrylic washes. Use a rust color with a black wash over the top. Practice the effect on some scrap material. We have found it to be quick and convincing. Try this technique on your next project.