For chaffing on the backside I have found baby wipes, the non alcohol type, work well for preventing any discomfort. The problem with some chaffing is the build up of salt crystals from sweat. If you are going to sit after a long sweaty hike then take a moment to find some place private to, well... "Wipe" away the sweat with a couple of baby wipes. While this might be a bit of a hassle it to me is much easier and more comfortable then having a "greasy bum" I found that twice a day seems to keep away the chaffing. Once before lunch and once before dinner. I am still pretty new to long hikes tho and have found that with time, and I assume toughening of my skin that I can go much longer without chaffing.