Can track be ballasted after it is installed?

By all means, for added realism, ballast should be added to your layout. But be forewarned - this is not a simple task. Several good brands of ballast are on the market today and are available at your local hobby dealer. Woodland Scenics makes a very good grade of ballast in various colors and in the proper size suitable for N-scale use (the wrong scale can look very strange, so be careful not to buy HO scale or larger ballast). Spread the ballast evenly between the ties of the track, both between the rails and outside the rails. Use a soft brush to move the ballast off the ties and to spread it evenly between them. Some brands of ballast have the binder (glue) already mixed in while others require a separate application of glue. In either case, use "wet" water to set the glue smoothly into the ballast without moving it. ("Wet" water is created by adding a few drops of liquid detergent to ordinary tap water.) The water, or water-and-glue mixture, should be dripped gently from an eyedropper and when dripped onto the dry ballast it should run into and around the tiny rocks rather than form in a ball on the surface. Do not disturb the ballast until the glue has completely dried. You might want to experiment on a siding until you feel comfortable ballasting the mainlines. After the glue has cured, examine your work and be certain that no ballast has piled up on the inside of the rails. Such a build-up will cause derailments.