Scrub the barrel with a stiff bristle brush and perhaps kerosene to remove the beeswax and oil. Then rub it down hard with a supersaturated solution of baking soda and water. Then pour several kettles of boiling water over the barrel (plugged,of course). While it is still too hot to touch, rub it down with a thick towel and motor oil. That's how I treat LMF browning solution. It is very aggressive and continues to work until it is used up. There will be no damage to your brown, though it may be coarser than you had hoped. Every day over the coarse of a week, rub it down again with the oily towel. You'll get brown rust on the towel. Eventually, it'll stop.
Others have posted their methods in the past...you might do an archival search to see what has been said in the past.