I've used some leftover plastic rock here and there. The plaster bandage forms the basic landscape over the polystyrene and bits of old stuff, then once it's set I layer some filler over it and then smooth it out with a very wet brush. It takes a while to set hard and is prone to crack a bit. If it does I just fill the cracks with another layer of filler. I try to make the landscape as though the rock and earth has been eroded by nature, principally water.
Tryfan Junction Station from the footplate of Lyd
I've had a very busy weekend in the 'real' world so haven't had much chance to progress, however I have built and painted a water tower for the station.
The basis of the water tower is a Unit Models resin casting but it isn't tall enough as nature intended so I've added an extra layer to add height. This is originally a Talyllyn job with a wooden trough to fill the loco but that is no good for me so I've made a pipe with a valve and a more traditional fabric 'bag'.
It ends up on the wrong side of the loop so I will need to add a facility on the 'up' line. It will need a pump to get the water to it which is an excuse for some sort of waterwheel and pump arrangement.