Spread dropcloths over the flooring and large pieces of furniture in the room.
Distress the walls so they look rustic when you paint them. Do this in a variety of different ways, such as hitting the walls lightly with a hammer to create indentations, hitting the walls with a screwdriver to make a randomly shaped dents or striking the walls with a chain. Be careful when you do this because you don't want to damage the walls structurally; you simply want to alter their appearance.
Prime the walls with acrylic primer to ready the wooden walls to accept paint. Use a roller and paintbrush to apply the primer and allow it to dry completely.
Mix 1 gallon of acrylic paint with 1 pint of mineral water. Water thins the paint a bit, helping it to appear more like a glaze and accenting the distressed wood effects even more.
Apply a coat of paint to the walls, using rollers and paintbrushes and allow the walls to dry completely. Apply a second coat and allow it to dry completely.
Rub sandpaper onto the walls in various spots to remove some of the paint and help the walls look even more distressed.