How to make a "wooden" sign out of cardboard?

Paint the cardboard a beige color using acrylics. Let dry then use a darker brown on it and cover the whole thing then while it is still wet take an old hair brush and glide it down the length of the cardboard and kind of a wavy motion, this will make like a grain effect on the cardboard and you can also make knots in it using the darker brown and some black. When you are finished just let the whole thing dry.It will look like wood.