I know a few have been asking for this so here goes.
As you now know, the layout is built on high density foam, the advantage of this is you can now add foam to build hills and curve the foam away to create valleys, gullys, drains and gutters. At this stage all we have is track laid on a flat surface, now the ground is rarely, if ever flat. The most important thing to think about is the formation of the land, land rises and falls in all directions. When you are doing this, try to ignore the track without forgetting about it completely. What you’re trying to achieve is the line cutting through the landscape. Look at photos and you can see where the railways have made cuttings and land fill to build the line to give it steady grades. This is an important stage, it really forms the basis of your scene. The exciting thing here is, as you’re creating the shape, you will start seeing where to form roads, water courses etc. Which really spurs you on to keep going and your layout will start to look like something from the real world.
A few tips here, everything is easily repairable so don't panic if what you have just done doesn't look right. The railways made banks and cuttings to specific angles so do some research into this and make allowances for adding plaster, dirt and rocks. Print photos out and stick them up to give references as to what you want an area to look like. Too much info is never enough so keep collecting.Next step is to paint the foam, colour isn't that important here but choose one better then what we did, an earthy tone is the go but keep it on the lighter side. This also helps to seal the foam and stops those white flaky bits turning up.
Now there is no need to plaster the whole scene, this would add to much weight and is only necessary were you want add fine detail. The cutting is one such area to be plastered as you need to add the wash out of dirt where water would have run. Now you could go nuts here but on this occasion we choose to keep it subtle. Mix up your plaster so its nice and pasty and have a clean bucket of water handy. Add a bit of colour dye to the plaster to get rid of that stark white colour, wet the area and apply. As the plaster is setting grove out the water course, making sure to not get it too uniform. This is also a good time to add very fine dirt so to get some texture. After it has dried I used some acrylic paints to get a good base colour but don't make it uniform. Paint in a mix of browns,reds and orange. Then add dirt to the wet paint in the colours your after. See Chuck or collect your own.
With colour its all about blending many tones, uniformity is a no-no in the natural world. So now you need to think about what came first, eg, dirt then rocks then dry grass then green grass etc etc. Your particular application will most likely be different to mine so use these as a guide. 
Once the dirt is glued and dried it is tricky to get the glue down for the grass as it can clump the dirt up, so thin it and don't over do it. When the grass goes down the same rules apply, blend colours and work from the ground up. The dirt is important as the grass should be patchy, look under the trees in the above photos, you don't want a carpet of grass. The electrostatic grass is really the only way to go, there is still a place for the flock but not like it used to be.
At this stage you can start to add the detail, fences, bushes, trees etc etc. The one thing we did try was the grass tufts from silflor. These are fantastic and bring realism to any scene. Once again you can see, build from the ground up.
I focused on the bridge module for this post and I think you guys can get an appreciation of how we went about things, it was enjoyable to do and to be honest we could continue adding to these scenes but overall, I am very happy with them.
Cheers
