If one is in a place with no clean water available, one may wash with whatever is available. For example, if one slept on the beach and there is only the salty sea water one may wash their hands with it and make a bracha. In a situation where there is no water at all, then one should wipe their hands on something hard. However, being that this wiping is in place of washing with water, one must wipe everywhere the water would reach i.e. the entire hand. Therefore, a dry towel or garment would be easier to accomplish this and perhaps better to use.