I think I would try the material painter and use the "blend color with texture" function as well. Select a grayish color to overlay over red vertical siding and I would think it would come out kind of washed looking. I've successfully created a driftwood color that way.
Another thing I will do in these instances is create my own custom material. Google 'faded red barnboard' to see if you can find an image with the look of what you're after, then import into Chief, adjust as needed and add to your user catalog.