I'm with a lot of other posters here. Bench grinder wire wheel is a nay-nay. And rust is NOT patina. Evaporust is certainly my favorite chemical solution, and I've tried them all (vinegar, oxalic acid, Coke, etc etc.). I've also found a small handheld wire brush with a long bristle bed to be useful in certain situations.
One problem that can arise with de-rusting procedures is that it removes the rust inside the below-surface pitting, leaving the surface very obviously pitted. I've had wrenches that weren't all that bad-looking that after the Evaporust were filled with obvious pits, and I regreeted not taking a more tedious hand-cleaning approach. A cleaning process that addresses the surfaces while leaving the filled pits intact can make for a smoother surface with the top of the pit rust getting kind of "polished".
As for value, it depends upon the amunt of rust. Removing surface rust without harming the tool definitely increases the value. But if the tol is heavily rusted, its value is probably already destroyed as a collectible, so you can't really hurt it by taking more extreme measures.
As I often mention, however, is if a wrench can be documented as having come from George Washington's carriage house, or something crazy like that. Doing anything to that kind of artifact will harm its value.
