Well, they put them through an apple scrubber. If the surface dirt is mild it just consists of brushes such as in the attached photo, but if the condition is really bad it consists of a water bath, typically with a detergent/disinfectant such as Tsunami 100. This process removes the natural wax on the apple skin, so they dip them in carnauba wax to allow them to be polished again.

I've seen home-made contraptions consisting of a expanded metal drum that rotates on an angle as the apples are poured down it and sprayed with water prior to cider pressing, but I don't think that would serve your purpose.

Wow, thanks applenut. I really had no idea.
So there isn't a preventative anti-fungal spray? I wonder if Rally WSP would work, since it is a fungicide (I use it successfully for CAR prevention)?

Captan works against sooty blotch and flyspeck. I found that using Immunox alone does not deal with these fungi. This year I used Captan and Immunox together a few times and my apples are clear.

Two years ago with the bumper crop most of us had, my apples were seriously infected with sooty blotch--so I hesitated to give them away and scrubbing each apple was too onerous a task. I vowed then to find out what needed to be done, and this year I had success. Captan may be hard to find, but I bought some on Amazon, and will be ready next year to treat scab ( I think).

I'd be real careful with apple scrubbing machines if I were a commercial grower. Those two growers who had the disease on their cantaloupes from a washing machine have just been indicted on felony counts.