Mineral spirits will clean shellac without damage and the test is certainly warranted. One part of this though is how much old wax and what kind are already on the surface. A lot of people are fond of liquid waxes often and this can really build up and cause some weird problems, even with identifiction. It really helps to see--and feel-- the finish. Nice to have a couple of people answer, isn't it.
Jules, please give it a quick cleaning and not a "good" cleaning, if you use water or anything with water in it. This is one place where a little can be too much. Do small areas and watch the drips and runs like you would with a finish.