I too work everyday in a big rig shop. After 5years(in Oct), I still dislike rivets, and cars don't seem all that big anymore.
I can't really say as I've seen what you are talking about, black that transfers when you sand it. Except on new aluminum parts like side extensions which usually come with an oily coating on them. Usually the corrosion is a salty looking white.
I'd wipe down with some wax and grease remover, and when everythings sanded, get epoxy primer on as soon as possible. Aluminum will still corrode exposed, but can't really see it like on steel. If corroded, paint and primer won't stick. Thats one reason you see so many using etching primer that work with a lot of aluminum, even though I feel its far insuperior to epoxy.
What works pretty good for cleaning up corrosion around rivets is a 1 inch green 3m bristle disk-plastic with the little fingers. It will get up tight to the rivet. Then feather out well with da and prime them (primer applyed smoothly as possible). But you need to do a good job feathering them and prime, or likely you will have rings showing when its painted. Also, be real careful sanding around rivets. If you hand sand with like 220 around a rivet or circle with you da, you will likely see rings or scratches. I don't know why around rivets are so fussy. Your best sanding the flat areas, and where you can get between rivets, but safest to scuff the rest of the paint or primer around rivets with a scuff pad to lessen chances of scratches