The only way I have found to get stain out of a bottle is by tumbling it. Putting oil on them will only hide it and if you try to sell the bottle with the oil on it someone might think your trying to hide cracks in it. The only time I have seen polyurethane on a bottle was over a paper label in a box of local bottles I bought. People did not like it at bottle shows. But then again you got guys who do not buy tumbled bottles either. Stain on bottles is just a part of life in bottle collecting and I have a tumbler.
i have tried bout everything , nothing helped ,if its on the inside nothing might not help,if its on the outside if you try rubbing it off it might make it worst,what ever you do that wood take the stain off the outside might scratch and haze up the bottle bad , maybe someday somebody will come up with the magic mix, oil or spray will hide it, glenn