Don't know for sure if this will help, but we found a couple of those barns in Shady Valley (among many other places in East Tennessee) and a sign at one of them that said referenced "quilttrail.com". I also have a guide for quilt barns titled "Appalachian Quilt Trail." And several years ago I printed maps from:
http://vacationaqt.com
I think there are some specific size requirements to participate in one of the trails, but I really don't know how to go about finding out what they are if one of these internet addresses doesn't have the information.
If you haven't done it, it is a lot of fun driving the highways and byways looking for these barns. A wonderful excuse to see some truly fantastic country.