[header] How to remove wallpaper with the dif method [title] Perforate the wall. [step] It is important that you do not " score " the wall, as this will damage the wall and cause the paper to come off in small strips. Specialized tools are available at your local hardware store. 
Look for tools which have spur-like wheels on them. These tools will perforate the wall with thousands of little dots, so that the dif can soak in.