With a couple of rags, a dry brush (with soft bristles), white vinegar and water, you can get most rock salt stains out of clothing. Start with 1 tablespoon of white vinegar mixed with a quart of water. If you need to make it stronger, you can.
To clean clothes that are water-resistant, dip a cloth in the vinegar water mixture and rub the spotted area. If it doesn’t come off, gradually add more vinegar until it comes clean. Then blot the item dry with a clean cloth.
For other types of clothing, let the salt dry. Then brush it off with a brush that has soft bristles. Make sure that if there is any mud, that it is completely dry also before you brush. You don’t want to work the mud into the fabric. Now, you can put the item into the wash like usual. If the clothing is a delicate fabric, we recommend sending it to the dry cleaners.