One word: Lantiseptic. Buy the 50% lanolin version, not the 30% version. I just finished Paris-Brest-Paris. 765 miles in 88:45. My butt was pressure sore, yes, but NO chafing and no broken skin. That stuff is tenacious. It stays where you put it. . My friend Cecil calls it butt spackle! I wouldn't ride an ultra without it.