It's actually not the salt that is the important bit, it's the solvent, isopropanol.
Salt is really useful because it is not very soluble in a solution of 70% isopropanol, which is your average rubbing alcohol- some WILL be dissolved in the water, but you will still have salt crystals in there, and they act as a gentle abrasive to clean your glassware. The resin is further softened by, and ultimately dissolved into, the isopropanol, which functions as a non-polar solvent (water is a polar solvent).
A bottle of rubbing alcohol is like a buck... go look under the seat of your car and you will find enough change to go buy some!