I couldn't find the actual tutorial on how to do it so I just made it up from what I remembered.
1. Draw your picture on the sand paper in crayons. You need to make the wax layer quite thick. I had to go over Auron's lines a bit harder after he had finished.
2. Place a piece of cardboard inside you shirt so that the colour does bleed through
3. Place your sandpaper picture face down onto your tee shirt
4. Iron over the back of the sandpaper for about 30sec.
5. Carefully lift the edge of the sandpaper to see that the picture has transferred. If not iron a little longer.
6. Put the shirt in the dryer for 20 mins to set, or use a hair dryer if you don't have a clothes dryer.
Note: wash by itself the first time you wash.
What Auron enjoyed most about this activity was drawing on a different texture. Lili loved scratching on the sandpaper and rubbing it together to make noise.