I used to have the same problem. I know this is going to sound odd, but there is a product that I swear by. It is called "Bag Balm". It is in a green tin. It's original intended use was to be used on dairy cattle, for chafing. They sell it in drug stores, and I think that I have even seen it at Target. Many people use it for diaper rash on their children. If it is good enough for a baby's butt, it will be good enough for your own gear.
I bring it with me on the trail. Apply it in the morning, and you should be fine for the rest of the day.
Tre