This session started by scuffing the contact areas of the left wing's lower skins with a scotch-brite wheel in my powerdrill. Then I used my bench grinder to thin out the material in the overlapping corner where the two skins meet, and rolled the leading edges with the edge-rolling tool. After that, I took the skins over to the DRDT2 table to dimple all of the rivet holes. A quick wipe-down with acetone and was then followed by a quick spray of self-etching primer.