I would not use any acids. Especially the fancy ones you can't just buy at the corner store. The ones with Hammett Values below negative eighteen. Sulfuric acid is negative twelve. Fluoroantimonic Acid is negative twenty eight to thirty. It explodes with contact with water. Fun!
I would use Spic and Span, or the generic purple desgreaser equivalent.
I would use bleach.
I would not mix the bleach and degreaser and use that. Although it will clean brass drains and truck wheels FAST. Eats the scale off of mineral deposits around faucets as well. Do not breathe the vapors!
The frosty clean is the metal being etched and removed, a bad thing for most firearms, especially bores.
Acids (normal, non flesh eating sorts) can also dry and react to leave moisture attracting salts. But bleach can do this too. A good rinse process should be employed.
I like the solvents that act like lubrication if they are missed. Or like brake cleaners that evaporate from the surface. These some times leave residues though.
The painter's section of the local home repair store is a candy aisle! Acetone, Xylene, Methel Ethel Ketone. All in gallon jugs that will fit a whole pistol when the lids is can-openered off.
Just be sure to test. Xylene loves plastic, a lot.
In fact most things that come in metal cans love plastic, and most things that come in a plastic jar will love metal, to death in most cases. A good rule of thumb for the layman, like me.
