For the window, I used the same technique :i.e. I draw the pattern on the acrylic and remove the parts I want to be seen on the window then I  spray paint. When it's dry I remove the paper from the acrylic, it looks quite realistic and it allows to add very small details. I didn't like cutting very small pieces of wood to make the separations on windows.
Then I painted a first layer of grey on the roof and tried the window. It looks OK.