I revived this thread to see if anyone else had thoughts to share on the Colonel's secret blend of herbs & spices.
To that end, allow me to share what I have concluded after taste-testing a lot of "interpretations": The ultimate secret is the use of a pressure fryer. I have three of various sizes, two of which are actually rated to pressure
fry.

:
One may enjoy the use of italian salad mix or dry tomato soup in baked chicken, but I found both brought their own unique flavors to the recipe while not approaching the KFC's unique taste.
Unfortunately, adding
significantly more salt than one or two teaspoons per two cups flour does make a difference. MSG (as called out in many versions) would probably help, but that stuff literally gives me the jitters.
One story has it that Harland Sanders lifted his recipe from a neighbor named Eula Gordon. That recipe had promise, but it is either folk lore, or the Colonel ended up lopping out most of the tremendous amount of paprika specified by Ms. Gordon.
So far, my best recipe for pressure fried chicken coating incorporates a lot of salt & pepper, some various spices, and
5th Seasons Poultry Seasoning. Walmart used to sell the blend but stopped for whatever reason. And yes, it was this specific brand. Other brands made the mix taste quite different.
Being somewhat obsessive about little things like what is in a given blend of poultry seasoning, I scowered the Internet collecting everyone's recipe for poultry seasoning. Comparing the recipes, I could draw no conclusion as to what set
5th Seasons apart from the rest.
So now there are two culinary mysteries - What is KFC's recipe, and what is
5th Seasons' recipe.
Anyone else care to share interpretive KFC recipes?
Tom