Yes. Baby powder is a simple & effective product. I prefer the non-starch materials. Placing starch on the moist skin of a baby is like setting out food for germs. Beware that babies have developed pneumonia when they inhaled quantities of talcum powder in a changing table accident. Like any effective product can cause problems when not used correctly.
Yes. Baby powder is safe for babies, but very often, diaper rashes will respond better to moisturizers. Moisturizers help provide a barrier on your baby's skin, which both allow a rash or irritation to heal and prevent further rashes from occurring. Any rash that persists for more than a few days should be evaluated by your pediatrician.