The best invention since washable crayons!
My children are older now and finally past the age of writing on the walls or furniture (mostly). But when they were younger we went through the "use the walls for art" stage with all five of them. My walls looked like a graffiti ally from about three feet down anywhere they could reach. Did I mention our walls were painted with flat paint. So, even with washable crayons, it was nearly impossible to get it off without removing the paint with it.
Then I found Mr. Clean Magic Eraser and this stuff is amazing. You just dampen the sponge and wipe down the wall. Crayon wipes off like chalk on a chalk board. It even removes pen. My husband came home and thought I had painted the walls. I am truly amazed with this product. I still keep a couple boxes on hand for those scuff marks and dirty hand prints that end up on the walls..... mysteriously!
It really is this easy!