Baking soda works wonders for getting rid of babies diaper rash and you can either apply it to the babies bottom with a washcloth or you can put them in a baby bath or bathtub with some baking soda and allow them to soak in it.
You can mix 2 tablespoons of baking soda with 5 cups of water and then use that washcloth or even a sponge to clean your babies diaper area with.
You can also just put some baking soda into the bath water and let them soak in the bath water to help clear up the diaper rash.
After cleaning the babies diaper area let them air out without a diaper for awhile.