I used to get chafing on my inner thighs from my underwear. I tried some different things and finally figured out just not to wear underwear during the warmer temps and it worked fine.

In the winter, I wear tight long underwear or at least that base layer type underwear that goes down your legs a bit.

Both of these measures have pretty much eliminated the problem, that was very irritating before that.

If your chafing is near your anus, I would say dump a bunch of baby powder down there or you could always put moleskin there as a last resort...that might feel odd but maybe not as bad as the chafing.