Before you immerse yourself in the process of creating the scenery for your layout, take a moment to appreciate what you have already accomplished, and the value of all the planning you did before that first piece of track was spiked into place. You are indeed quite close to achieving your goal of building a wonderful layout. If you made a model of the layout during the planning stage, hold it next to your layout to see where the hills and valleys will be. If you're not completely satisfied with the way the electrical circuits and devices are functioning, now is the time to make final adjustments because the likelihood of damaging scenery is great if repairs are needed later.
In the earlier Greenberg book that I wrote, the primary scenery technique used plaster of Paris and paper towels, a particularly messy process. In the intervening years, several scenery techniques have emerged that both speed the process of scenery creation and also lessen the mess. At the same time, these newer techniques have resulted in greater realism.
That said, there are different approaches to the character of scenery. In Europe, static grass is quite popular. In a casual hobby situation, the static grass is applied from a plastic container onto a layer of latex paint. For the serious hobbyist, the grass is applied and then a large electromagnet is used to make the grass material stand on end. Given the general appearance of real-world European scenery, the static grass produces a realistic outcome.
In the American market, there are those who use static grass, but most use ground foam, which is literally ground up pieces of foam, with the name ground foam also being a useful description of the product’s purpose (ie, foam on the ground). The primary manufacturer of such ground foams is Woodland Scenics, although there are other companies. Most of what is written here has Woodland Scenics products in mind because they have produced a complete line of products necessary to create a realistic model railroad scene, and they have the depth of distribution necessary to insure that you will be able to find it at your train dealer or online.
At this point, you will need to take steps to protect your completed layout work from damage by the materials used in making scenery. This means that the tracks must be covered with masking tape and the structures removed. As you remove them, pencil in their base outlines on the layout board to remind yourself where they were as you install the scenery. Since it is usually not feasible to remove bridges and ramps, you will need to mask them as much as possible.
You will also need to remove the catenary wires. (Did I just hear a noticeable groan?) Sorry about that, but it does make things much easier in the long run. The wire is left in place, however, where tracks go through tunnels, and the whole section of track and overhead wires should be covered with a tent of tape and paper. Whenever possible, the catenary wire must be removed, along with the cross spans. The 8914 masts and any terminal masts can be left in place, but must be covered. Since you have gone to no small effort to adjust the wires for proper operation by skillful bending and shaping, you may want to mark the individual wire pieces with a small, numbered piece of masking tape. Then, write a corresponding number on the masking tape covering the track to help reposition the wire after the scenery process is complete.
These efforts really are necessary because most scenery techniques are messy. A good place to work is in a garage or basement where the concrete floor can take the brunt of the action. If that is still a problem, newspapers can be used to cover the floor. Plastic sheets also are effective. Carpeting does not clean up well, so an ounce of prevention is definitely called for. In particular, keep in mind that the plaster of Paris mixture you will be using acts like a bleach, leaving lightened spots wherever it has landed.
That said, there are several ways to approach placing the scenery on your railroad. Your first concern is deciding how you want your scenery to appear. If you are modeling the Santa Fe in New Mexico, your layout will appear differently than it would if you are modeling the Santa Fe in Illinois. Once this basic decision is made, your palette of colors, trees & shrubs, types of rock and such will be decided and it is just a matter of putting in the basic hill forms and then detailing them.
I have listed three approaches to model railroad scenery. One is the Woodland Scenics SubTerrain System approach to model railroad scenery, which uses plaster cloth and plaster rock castings over forms. This is really an evolution from the traditional plaster of Paris and paper towel technique, and is part of a large concept of model railroad construction; the track support portion of this technology is discussed in the Layout section. The second approach uses blocks of foam to create the hill forms, and the third approach is the earlier method of using plaster of Paris and paper towels.
Making scenery happen is an enjoyable process, and a forgiving one. If you make a mistake, it is easy to cut out and remove what you don’t like, or to cover the mistake with more scenery material. You will have fun with this.