Because I like to avoid difficult things, I am going to work on the ceilings on this side of the dollhouse, before I embark on the staircase delima.
The best way to work on ceilings is to turn the dollhouse upside down, but because this model has a protruding chimney, that's not an easy thing to do. I used a small wastebasket, so I can put the chimney inside and I can keep the dollhouse upside down.
I used ceiling paper on the hallway and kitchen, but used a shiny, metallic paper for the bathroom ceiling. Remember that these highly textured papers do not patch easily, so make paper templates of your ceilings and then use them as a guide to cut your ceiling paper with.
While you're at it, you can install the ceiling trim for rooms that already have wallpaper installed and touch up any paint that is visible at this angle.