There are several ways to use baking soda to clean up crayon marks. The first option is to apply baking soda to a moist sponge and rub it on the wall to remove the marks.
Another method is to add a small amount of toothpaste directly onto the marks, then apply a mix of baking soda and water to the toothpaste using a toothbrush.
Once you have successfully removed the marks, rinse the treated area with a clean, damp cloth to remove the baking soda paste and residue from the wall.