Gilmore:
I'm afraid I can't add much to what you already know. Perhpas the ebst way to deal with chafing is to keep the area powdered. I would stay away from cortisone creams, because they have not helped and because they may redden the skin further. If I were you, I would pay as little attention as possible to the redness, and just treat the itch with talcum powder and use of a light moisturizer to deal with itch.
Best.
Dr. Rockoff