Read the
Wikipedia entry on "season cracking" to understand where the warnings came from.
We had one fellow post who had used Brasso to polish a bunch of linked surplus ammo he'd used as a wall decoration in his room in high school. It got put away in a trunk with other stuff of his when he left home. 20 years later, he retrieved the trunk from his parent's place and opened it to find powder all over because the brass had corroded through.
20 years is a long time. What I found interesting was the ammo wasn't repolished in the time it sat in the trunk, and though I don't know how many times it may have been polished prior to that, the point is that the corrosion damage continued to progress into the brass on its own over time. This suggests that if you did use Brasso or another ammoniated polish, you could be putting the brass on a countdown clock that will eventually run its time out, and would therefore want to use the ammo to the end of its reloading life as quickly as possible and not keep it for years.
What's absent from the above, is whether the use of non-ammoniated polishes or liquid cleaning in safe chemicals will stop the corrosion process or not. I just don't know.
To make safe cleaner, just mix up a slurry of water and
diatomaceous earth, which is sold for killing insects and is a toothpaste polish, among other things. If you want something coarser and faster, buy
white automotive polishing compound, or buy the
powdered kaolin clay that is its abrasive. Take a tablespoon and add enough water to thin either one out to liquid polish consistency and add it to your media.