The lower wings were glued in place. To get the right dihedral angle (which is rather important for the outer wing struts to fit when the upperwing is fitted), I put small wedges below each of them while the glue was curing.
Then, the lower side was painted light blue (I used Humbrol 65). I then made a mix of 30 and 89 to get the upper blue-green. I poured a bit of it in a paint jar and added one or two drops of white, then sprayed the wings and stabilizer. After that, the ribs were masked with thin masking tape stripes, and the final darker blue-green was sprayed over.
When the stripes were removed, the ribs were too visible, so I made a light overspray with blue-green to blur the ribs a bit.
The red arrow shows the lip around the winter cowling, which was made from strectched sprue and glued with CA in 3 or 4 steps.
This is one of the typical details which give those birds their "steampunk" look I love.