I use this method for smaller amounts, have not tried it in big yardages.
For a bucket size, I would use 1/2 cup of vinegar, and 1/4 cup of salt. About 3 tablespoons of baking soda. Let them have a good soak, even over night, I have left mine for, but not necessary. There is a certain amount of washing out of the colour, I have found that coffee is the best for staining fabrics to give them that old aged look.
Gal