I used to be a city mail carrier in Omaha NE.  Hot humid days like we are having now, I would suffer from it really bad.  I went through a LOT of cornstarch, and it worked pretty good.  After I changed jobs, I really became tender in that area, and anytime I wore jeans, I would get it bad.  I switched to boxer briefs about three  years ago and I've never had any problems with this since I started wearing them.  One day I ran short of the boxer briefs and pulled out an old pair of briefs, wore those.  I didn't make it two hours and I was galled just like I used to be.  I'll stick to the boxer briefs, much better product.