I masked the areas that I didn't want to be covered by my mess. I used the brown masking tape. I think I will try the blue for the backdrop masking next time. I had paint pull off on the backdrop. Luckily it needed reworking. I would also hang newspaper to cover the whole backdrop.
I covered as much as the finished half as possible. I spill things easily.
In masking the track cover the whole ballast area. Press the masking tape to maintain closure. If you drop plaster or paint it will go under the tape unless it is closed, Believe me.
The first step was covering the areas that would not be changed.
I left a small strip along the rockface in the cut because it was going to be reworked.