This is an old topic I know, but I just can't seem to achieve this effect. I paint the cardboard (cereal box) with brown acrylic, I wait till its dry, about 10 mins. Then I apply the thin layer of white elmers glue, I only wait a minute or 2 for this step cause it seems to be starting to dry at this point. I then use this light grey acrylic paint over it. It does look slighly weathered but not really that great or cracked. Maybe my timing is wrong or something on waiting between steps, I'm just not sure. Any advice would be greatly appreciated.