A key variable is to reduce friction. Make sure the saddle is not too high. Your hips should not rock from side to side when you pedal. Adjust the fore/aft position of the saddle so that you don't slide foward or backward when riding with no hands. A leather saddle like Brooks Imperial, Pro, or B17 is slippery and can significantly reduce friction and moisture.
Stand for 15 seconds every few miles to restore blood circulation to the bottom. Tilt the nose up a little so that the sit bones are supported at the widest area of the saddle. This will also alleviate pressure on the crotch.