Clean with GP solvent to take off printing then Prepsol(Wax and Silicone Remover) to take of the oily layer on the sheets. Use a file to rub the edges of sheets and parts smooth, then run the deburrer along the edge. I went over the face of the sheets, flat on the bench, with a 1/3 sheet orbital sander with green scourer pad for the primer to key onto, just enough to take the shine off them.
Get couple of off cut pieces from some sheets, prepare them like parts, drill a row of holes through them for rivets. Put the black stuff on each surface. Let it dry, then rivet them together. leave it for two or three days, drill out the rivets and then see how hard they are to move apart. The black stuff stops the parts moving on the rivets causing the rivets to work loose.