Kentucky Common

Bought a kit awhile ago from...I forget who. but it was the grain bill for a Kentucky Common. Basically its an American Brown recipe with a portion soured mash added back in after sparging and main mash are complete. Anyone ever made one before. Or tips on naturally souring a beer?

I brewed this Kentucky Common a couple years back. Following the directions, I mashed 20% of the base malt around 158 and then left it covered on my warm windowsill for 2 days until it developed a very sour milk/cooked corn smell and taste. Then I added that to my regular mash and sparged, brewed, etc. as usual. I've used that same method of a long, warm mash to make a Berliner Weiss and a Gose since then - works pretty well.