It all depends on the kind of chafing you have. I use cornstarch if it's prickly heat. For other kinds of chafing, I make sure the area stays moisturized and use the Aveeno (or knock off brand) body wash.
If it's a yeast type thing, I use the Aveeno body wash and then splash it with Sea Breeze for sensitive skin. It burns sometimes, but it knocks the fungus out. I suspect this is because it's an astringent and makes the environment inhospitable. Sea Breeze can also work to help cool prickly heat. It's good stuff and I always keep a bottle in the medicine cabinet.