Hawken you have hit the nail right on the head. Water to dissolve the fouling (salts) then an oil to protect the bore. I do not know of another liquid that will dissolve a salt. Water is inexpensive and easily obtained everywhere.The problem is there a misunderstanding about what it means to "clean" firearms. Modern smokeless propellants and non-corrosive primers means anything, including doing "nothing" will work pretty well. However clean it "looks", there is a problem when dealing with corrosive residues.
Blackpowder is a completely different animal, now interestingly enough, the only chemical that dissolves salts as a class, is WATER. Somebody can run 950 oil soaked patches down their gun and it will never dissolve or remove all of the burnt powder salt residues embedded in the bore nooks and crannies and elsewhere. It will happily corrode the bore over time underneath a thick the layer of oil or grease. It won't matter how "clean" it looks. Oil does not neutralize salt!
That's why "hot soapy water" has long been the only way suggested to clean firearms using corrosive ammunition, it isn't because people are being cheap, or sentimental, it must be water or water based. It's basic chemistry 101, not opinion or stubbornness.
I started this racket in the days of corrosive primers and caps. Warm water and lots of it kept my original Colt 1851Navy and the bore of a rifle designed by a Canadian "the best battle implement ever devised" that I cannot mention here clean enought to keep my Sergent happy.
Respectfully
Bunk