Thanks to Cindy for this Frugal Baby Tip!
If you have extra vitamin E capsules around, puncture one and rub on baby's bottom. When my baby has had diaper rash, I've never used a "traditional" cream for her bottom. I've used a cream containing beeswax, Melaleuca oil, vitamin E, and a couple other things.
Or, you can use massage oil, too, or vegetable oil (which is virtually the same thing as shortening). Olive oil might be good, too, since it would not only coat the bottom, but has medicinal properties in itself, too.