1 slice white bread
1 piece muslin (or handkerchief)
First clean the wound. Fold the handkerchief along the diagonal. Place the bread on the handkerchief. Pour boiling water over the bread to thoroughly wet the bread but not dripping wet. As soon as the bread has cooled enough to be put against the skin, place over the thorn or glass. If you get the child to do this themselves then they won't get scalded. Tie the ends of the handkerchief around the foot to keep it in place and elevate the foot. Again, let the child decide when they can tolerate it. Encourage them try to do it as soon as they can put up with the heat. The hotter, the better. When the bread is cold, wring out the water and repeat with more boiling water until the offending object it ejected from the skin.