I'm all for straight up water, and maybe a little dish soap if really needed.
However. There are times, and weather conditions apply here, that I just really don't want to be messing with a bunch of water. (Though my little hose gadget from Dave Crisali makes this far more tolerable) Sometimes time, sometimes weather, is a factor.
So, what if we change the question slightly? What if we take the focus off cleaning, which water does just fine, and place it on the neutralization of the acids and salts that burnt black powder residue had that causes rust and corrosion?
What can one use as a quick swab or two, maybe a quick rinse and dump, that will neutralize these acids and salts?
We will go back and clean the crud later, for now we just want to eliminate the damage that crud can do.