yes, the salt "dissociates" or "ionizes" into free swimming Na+ and Cl- ions that the water molecules had pulled from their originally solid crystalline structure. You explained the concept accurately.
you said "water ions".. the polar water molecules are not considered ions. Distilled water...
grease won't stick on it permanently...
silver will naturally get an "aged" look from oxidizing in the air but for a fast effective process look for "liver of sulfur". it's a chemical that'll oxidize silver and give it an off-black colour.
other easier but less effective methods would be...