In this long session, I started by riveting the outboard flap hinge bracket into place, since I had previously finished all of the skin rivets in this area. I started to try to install these 10 rivets by using the hand squeezer, but quickly discovered I could only set about 4 of them that way. So I got out the double-offset #4 rivet set and got those rivets taken taken care of. Putting some tape on the rivet set and the spring of the rivet gun is definitely a good trick for keeping the offset rivet sets from rotating while you're working.
After that, I decided to tackle the remaining flush rivets on the outboard upper skin. I ended up placing the wing flat down on my two tables (skin side up, open side down) with a gap between the two tables so that i could reach up inside to buck the shop side of the rivets. Because the ribs face different directions, this was a good opportunity to practice riveting with my non-dominant hand. It was definitely a nice accomplishment to finally see all of these rivets completed.
Next, I got out the two J-channels that I had cut and match-drilled weeks ago and started prepping them for the next steps. I deburred the holes, smoothed the sharp edges, scuffed the surfaces, dimpled the holes, then primed the two pieces. Once dry, I slid them into place and clecoed them to the wing, with the proper overlap section. I had to check the annotated wiki instructions to be clear about the intended overlap, since the phrasing of which J-channel is "on top" has a different meaning here.
What's next? I'll try to finish riveting this J-channel in place, and then maybe set the wing aside so I can start the work to finish up the flaps and ailerons.