Wow! Everyone has an opinion and a method. I like the plastic brush. Don't know if it is easier than shaking a granular/water solution. Which takes more effort? LOL. And no one has mentioned where to get either bottle brushes OR the plastic brush. Hope to find out soon!!
Terry
I got a couple of very long and sturdy bottle brushes with brass bristles from a vendor at the Carlisle PA auto show last year.
When I got home from Carlisle, I took a vise grips and bent the sharp end around in a half-inich loop and squeezed it closed.
I use that brush in combination with Bar Keepers Friend (a cleanser powder) and some water.
Most metals are not hard enough to scratch glass, but check. I know that tungsten and chromium can scratch glass but they don't use those in wire brushes.
Brass will not scratch glass. Quartz sand will scratch glass but if it's just swirled around a bit in water, it's negligible. Just don't scrub on the sand with something.