Squeeze out a little mound of shaving cream and squirt on your dye.
Then, place your egg into the shaving cream and swirl it around. We left ours on for just 30 seconds or so. Rinse off the egg in water, and you're done! At the children's museum, they had plastic sheets on top of tables and just squeegeed off the shaving cream residue after each child was done. At home, I would use a rimmed baking sheet or plastic container to corral the mess.