I have smoked salt 3 or 4 times. I used sea salt thinking that the flatter crystal would give the smoke more surface to bond to. It turns the salt brown, but doesn't seem to leave much smoke flavor at all. I'm convinced that to get much flavor, one would have to make (or buy ) liquid smoke, reduce it to a powder, then mix it with salt. Either that or dissolve salt and liquid smoke in water, and let the water evaporate.
My concensus is , if you want smoke flavor, use wood.
Tim