Yeah, I actually read that cleaning with sand was forbidden in the French Army.
The thing with brick dust is that I do not know where to get it. I could just get 2 bricks and make dust out of them, but I read that you need a specific kind of brick dust, as most modern bricks are of different material or something. Supposedly using the wrong brick dust will cause the same effect as sand: (which makes sense to me) deep cuts in the metal which will wear it off and make it rust even faster.
The historical way would be to use brick dust, get a rag with a bit of oil on it, soak it in the brick dust and remove the rust that way. Corners would be cleaned with the "astic" a wooden scraper.
You would almost never take your gun apart, as it was not encouraged, parts could be lost (look at my missing spring...) or would break to quickly.