A little more history - and a ballasting problem

It turns out that a branch line south from Berwick and Wooler might have happened, even without the fictitious town of Belstone.  The Central Northumberland Railway was originally intended as a fifty mile line from Scotsgap on the Wansbeck Valley Line, through Rothbury, along the Coquet Valley to Alwinton, and thence over the Cheviots to Kelso.  The project was taken over by the North British Railway as part of its drive from Scotland into the North Eastern Railway heartland, but in the end only the first thirteen miles to Rothbury were ever built.  But had the railway reached Alwinton, a line from there to Berwick would have made some geographical sense, providing the North British with an alternative East Coast route from Berwick to Morpeth, within striking distance of Newcastle.

Meanwhile, back on planet Earth I have a constructional problem to resolve.  It concerns ballast.  Northumbrian branch lines typically used fine ash ballast, with the trackbed looking as though it was sunk into the ground rather than raised above it.  Within station areas and goods yards this material would cover the whole area, with no visible ballast 'shoulder' or cess between running lines.  So far all my attempts to reproduce this have failed.  I have tried fine blasting sand (much too coarse, and horrible stuff if a stray grain gets into a locomotive mechanism), flour (about which experiment, the less said the better), various combinations of glue, sticky tape and foam.  I even tried cutting out the shape of a piece of track in 2mm foam, but lost patience after about three sleepers.

One possibility is to embed the track in modelling clay, then use a stiff bristled brush to give the surface some texture.  I'll see if I can get hold of the materials and give it a try.