I've been experimenting with backscene materials, I finally decided on use of 3mm PVC foamboard. Unlike wood this has a very smooth finish and takes spray paint well, this was glued to the wooden frame with contact adhesive and kept it's subtle curves.
Track weathering was carried out with a dark brown powder pigment applied to each rail side, this was then faded in with a broad fan brush. Once happy this, along with the road/yard weathering was sealed with a matt varnish.
Fish plates were picked out with black powders to simulate grease.
Experimentation now starts with tree placement.