The "brown" stuff left by the soap (which is most likely mildly alkaline, which caused some etching of the 2024) is "smut", basically - alloying elements left on the surface of the 2024 after the alkaline etch removed some aluminum.
I would simply retumble them to get the outside texture match the other parts again, as for the smut, there is a very "laymans" sort of way, take a bathroom cleaning gel, the ones that remove rust, calcium deposits etc, some of them have chlorine in them, avoid that stuff (chlorine has a distinctive smell to it), using these cleaners as opposed to pure acids has the benefit of the gel to "lift" the smut, it will come off much much easier than just by dipping them in weak acids, some mechanical help may still be required, like a sponge or a brush.
The side effect of all this is that the parts surface is left very active, slight moisture on it and it will corrode quickly, may lead to ugly pitting, normally one would immediately follow with some sort of protective treatment, conversion coating, anodizing or at least spray with wd40.