Carl -- tried it as well. The dark spots/grime haven't really come out but If I can get a bit more life out of my FJ gloves I'll be a happy man. Am over in India and FJ gloves are more expensive (not that readily available). I tend to opt for Srixon as my backup.
miniwartmth, if you let them soak a few hours, more salt will come out and, as they are hanging to dry, the dark spots can be stretched a bit.