[header] How to grey wash wood [title] Lay down a tarp or dropcloth. [step] Choose a well-ventilated area to work in, and set down something to protect your floor. Newspaper is fine if the object is fairly small, but a tarp or large dropcloth will work better if it's a piece of furniture. 
[title] Sand the wood to remove paint and imperfections. [step] Use a coarse sandpaper all over the surface of the wood you plan to apply the wash to.