I didn’t believe it until I finally tried it. Grab a large large container, pour in a half gallon or so of white vinegar, throw in two pads of fine steel wool, cover, and let steep for three to four days or until the steel wool totally dissolves from the acidity. On day three the steel wool was still intact, on day four it was gone. Go figure.
The result is a dark colored, toxic waste dump looking leakage. Give it a stir and brush it on your wood heavily, letting it puddle, and let it go to work. Once dry, you’ll need to wipe the dusty steel residue from the surface with a dry rag to reveal what you’ve created. A good beating with a chain and worm holes made with an awl before I got started was worth the effort.
Believable weathered barn wood? Not as bleached gray as I was expecting, but after a few more coats it was as close as I was going to get using this method.