We just finished sponge painting my 10 yr old granddaughtesr that lives with me bedroom about a week ago. We had white walls to start with and she wanted blue walls so we just bought regular blue paint and bought a sponge at Walmart from their paint dept. (They had a lot of sponges to pick from) We had a ball doing it together ended up doing 2 walls, closet doors and wall unite. Turned out great. That was the first time we had done this.
My only suggestion would be don’t put the paint on thick on the sponge. Their isn’t any kind of pattern set just where ever the sponge stops. Hope this helps. If you have any other question just ask. Bobbie Jo