To clear up baby's diaper rash make sure that you change her as soon as she is wet. Wipe the entire area with a wash cloth moistened with a 50/50 vinegar-water solution. Let her bottom air dry if possible and dab on regular Maalox (liquid antacid).
The vinegar and the Maalox neutralize the acid from urine and the Maalox also dries up the rash.