Water spots can be tough because depending on the mineral involved you actually have a deposit of the mineral that adheres to the blade. I've found typical metal polish does not take off many mineral stains. I've used Cape Cod Polishing Cloths to remove them but the more you rub the more you will change the appearance of the metal. I have an assortment of watchmakers tools and they have a brush which is made of fiberglass fibers and it's small and precision enough to take stains off without harming gold wash only because you can go around the wash assuming of course the stains aren't over the wash.
To tell you the truth these days I live with the stains. They do no harm unless they are a corrosive mineral and only are cosmetic. Eventually when it's time to hone up the blade I'll remove them.