This process has been described before, but a quick run-through again will save members trawling back for it ~ if interested.
The track paint had made the track pretty rigid and so I separated sections leaving just the loop. It was then slid to one side out of the way and masking tape put where the point tiebars will lie. The long strip denotes the station platform edge (12mm from the nearest rail)...

Ballast is a mix of Fine Light Grey and Fine Dark Brown................. Neat PVA brushed onto baseboard, track laid and ballasted....

Care taken to ensure a 150" radius curve and a straight section after vacuuming off surplus ballast. Plywood and books weights...

