Making and finishing a wagon load.
Some wagons and many locomotives come with a moulded plastic coal load. To 'dress up' this load paint it over with glue (eg PVA) and scatter on real coal to provide a top layer.
Allow to dry, then tip off the excess coal onto a large sheet of paper, recovering the excess for re-use.
Wagons without pre-made loads do not need to be filled from the bottom with the crushed coal, the volume can easily be filled using a false floor.
Mark out and cut a rectangle of card or palsticard which will fit into the wagon.
If you want to make the load removable you will need to cut the rectangle slightly small so it will slide in and out, otherwise as tight a fit as possible against all four wagon sides is desirable.
Cut from the same material a set of supports which will, when resting on the floor of the wagon, place the false floor at an appropriate height, perhaps aligned with the bottom edge of the uppermost plank of the side, and glue to the underside of the false floor.
Many shapes can be used, but consider three cross-members joined by one longitudinal for good support. For removable loads making a two cross-member wide H shape set towards one end (though always reaching over the middle) will give a 'free' end which can be pressed downwards to tip up the load, making removal easier.
Paint the upper surface of the load unit matt black. If using a slow drying paint coal can be scattered onto wet paint to create a base load level.
Apply glue to the surface ready to add the coal and scatter on a good layer of coal making a raised heap if desired.
As above, allow to dry then tip off the excess. Repeat the glue process if necessary, or to add an extra coal in a certain area.
When happy note on the underside of the load which wagon it was made for!