In dry brining, course salt is used to draw water out of the meat, which hydrates and dissolves the salt, and then the saline solution is absorbed back into the meat. You can watch this is real time. Apply course salt to meat, put in fridge and observe surface of meat every 10 min. You will start to see water droplets forming around the salt crystals, which will dissolve and then be absorbed into the meat. This happens within an hour. All of this water is from the interior of the meat (osmosis), not the air in the refrigerator (condensation). You can put a little bowl of salt in your fridge and after 2 hours will not see any liquid forming (I just tested it).
Thicker pieces of meat benefit from dry brining for longer times (up to 3 days), so the saline can penetrate further into the meat. You can use a flat pan/sheet for brining or a wire rack. The rack has the added advantage of allowing air to circulate under the meat and helping the surface dry. So dry brining helps the meat retain moisture in the interior while also drying the surface. And as we all know, a dry surface promotes the Mallard reaction.