A tray of some sorts
Cardstock or construction paper
A toothpick, paintbrush, or spoon (something to swirl the paint)
Squirt enough shaving cream on the tray to cover the surface. Spread it around to make the surface relatively even, it won't be smooth.
Once you have your shaving cream on the tray, squirt some acrylic paint onto it.
Then using a toothpick, paintbrush, spoon, or something similar, zigzag gently though the paint to give it a marbled effect.
Using cardstock or cardboard paper cut out egg shapes paint .
Press your paper into the paint/shaving cream and let it sit for a few seconds. Remove the paper by lifting it straight up. Let the paint/shaving cream sit on the paper for a couple of minutes before squeegeeing it off the paper. Gently and smoothly squeegee the shaving cream off the paper. It will remove the shaving cream, but not the paint