I used liquid polymer clay to cover the tiny signs which were printed onto plain paper. I simply dabbed the liquid on both sides of the paper, smoothed it out with my fingers, and cooked these briefly on baking parchment paper. The smooth blue clay on the surface of the polymer clay door base was just a little too tidy for my daughter's taste, so I brushed liquid polymer clay onto it to finish, creating striations with the bristles.
This was an interesting first attempt and I learned a lot. I plan to build another with step-by-step photos but thought this was a pretty cool little thing, flaws and all.