This was how I did the walls of the hut:
1. Cut outline from a shoebox - sandwich 2 layers of cardboard with lots of white glue.
2. Cover both sides with drywall filler, sand level when dry with files and sandpaper.
3. Primer with Krylon sandable grey primer.
4. Apply salt crystals and airbrush over with white acrylic paint. Rub off salt when dry to create chipped paint effect.
5. Soak a paper towel with thinned black acrylic and rub on the white walls to tone them down.
6. Paint the bricks and wash with brown paint for grout.
7. Apply pastel rain streaks.
8. Complete!