I sprayed etch prime on sheet lap underside, and rivet lines and laps on the topside. Then painted black on both lap surfaces and allow to dry. All frame contact and frame sheet contacts are treated with black too. I masked the sheets so it looks a bit neater but I am the only one who has to look at the inside. It did take longer though.
Then build the frame and sheet it, then spray a coat aver the whole piece and the solvent in the top coat blends in the edges of the first coat but it gets primer under you rivet heads.
I used White and Grey in a 50/50 mix because the finish coats are all white.
Edit : I just reread what you typed and think you had it the first time sorry.
Still think you could build the rudder, elevator stabilizer and fin, flaps and ailerons in the lounge room while you are waiting to finish the shed! It will help your wife improve her adaptability and coping strategies. To be fair I used my mother's lounge room not my wife's and she had just moved to town to retire. So I was really only making it so she wouldn't change her mind and want to come back.