I have used the following method, and it looks pretty good. Remember to check out our guide to railway layouts.

1. Using plaster, make the area where your road is to be. Dont forget
to include wheel ruts…..a moist finger or other blunt device should
work ok.

2. Wet the road with water using a spray bottle

3. Take dry plaster mixed with dry pigment and sprinkle on your road
area. The water will activate the plaster and it will have a “powdery”
look when it drys.

4. add a little “brush” to the center of the road, between the ruts, as
well as along the outside of the road.