I use the Works toilet bowl cleaner, you need to use elbow length rubber gloves. I got mine at an auto parts store. The Works is very corrosive. If you get any of it on your skin or eyes, wash it out with water immediately. The Works is about as good as anything else I've tried. If I have alot of bottles to clean at one time I will take a 5 gallon bucket and pour one bottle (1 qt) of the Works into it and fill it about 3/4 full of water and let them soak, depending on how bad they are, from 30 minutes to 2 to 3 hours. And then I use a small brass chain, about a foot long, I got the chain from the hardware store, it is used for hanging lamps and decorations. I have another 5 gal bucket filled with clean water that I will rinse them out with. I will put the chain with a little bit of water in the bottle and shake it around the stained areas. You may have to do it several times, but it will usually take most of the stains out. If I only have 1 or 2 bottles I will pour the Works directly into the bottles and let them soak. After I'm thru letting them soak I will pour the Works back into the bottle to reuse. On the outside of the bottle I will use some scotch brite.
Dale
Dale