Very nice! I especially like the different shades of rust on the side of the locomotive's cab. Also the hinges and "peeling paint" effect at the front of the engine are very convincing. For future reference, most weathering occurs on the roofs of equipment, since they get rain wet, and the sun dried, over and over. Another area to rust and dirt up quite heavily is the trucks, wheels and under-body details like fuel tanks, boxes etc. They are constantly bombarded by ballast dust and it's "sandblasting" effect on them. By law, wheels can't be painted, and they are usually a solid dark rust color overlaid with dirt. Diesel fuel and lubricating oil leaks can also sometimes be seen down at the bottom area.
Track also looks much better when painted. The rails can be a flat, dark gray color, or solid orange rust on a seldom used siding. Often it's a combination of colors, like the turnout rails in the photos below.
I see you are using Atlas code 80 N-scale track. That track is made with several very unrealistic features, rails way too big, ties to short and too far apart, giant spike detail, etc. Painting, and ballasting, can do a lot to help the appearance of this track. A simple overall spray from a "rattle can" of Rustolem, or Krylon brown primer is an excellent start. Keep the can at least 18" away and use several light passes from different directions. Let each pass dry before making another one. Spray cans put out a lot of pain in a hurry! Too much paint can spoil the looks of your track.
Atlas makes a code 55 track that looks considerably better than their code 80 track does. However, the most realistic-looking flex track available by far, is Micro Engineering's. I use Micro Engineering N-scale, code 55 flex track. The tie size & spacing, smaller spike detail and wood grain of the ties, all make this track look very much like the real thing.
You might consider adding more rust to the rail box car. Those cars are pretty old, and most have plenty of rust. I'm not sure what you mean by, "but I have to sand the black paint off it first." It's not necessary to remove any of the original paint from a model in order to weather it. Most weathering materials, including my favorite, chalk, can be applied right over the original paint.
Hi Traction Fan, and thank you for the useful tips , I am fairly new to modelling trains and weathering. Your track looks great and well used ha ha . "As for the sand the black paint off" I was referring to the black hood of the switcher, as the rust color doesn't seem to show up well on a dark black back ground. I will work on the trucks and under body next .
I got a bottle of mud that im eager to try.