I have wanted to have a go at this for ages. I am doing these with a Year 6/7 class and so far, so good....although a little messy!
When the glue was dry, we sprayed a small amount of spray adhesive onto the owl and covered it with a sheet of aluminium foil (make the foil sheet slightly larger than the piece of white card). We then gently rubbed over the foil so that it adhered closely to the lines of dried glue underneath. To emboss we used blunt pencils to add designs onto the owl and patterns into the background.
Lastly we added some colour. We worked straight onto the foil with coloured permanent markers. If students wanted to make their colours lighter and a bit more subtle, we used a tissue to rub off most of the permanent marker as soon as it was applied.