The Bishkek 2nd Valkyrie, Part 4: Moving on

I moved on after my meltdown over the wing ornaments. I painted them white and that's how they will stay. I told myself it's just a model and I can always go buy another one..

Having resolved all of this, I started weathering the model. I intend to use the glossy coat and the oil paints, so before that I had to basecoat everything pretty well, including the basecoat wear and tear, using the granite foundation paint.
Using a green scrubber, I made tight scratches with the grey paint, all simulating wear because of speed, so all the lines move from the front to the back.
It's hard to keep them super straight and I did make a tool for this, gluing a little piece of scrubber to the end of a brush, but it didn't last very long. I also did some work on the parts that would get more dinged up and where people would walk or open up hatches.
The tail came out well.
so did the bottom, trying to keep it moderate and not go all out.
Here I gave the engines a basecoat
and added some wear to part in the middle.
After all that, I threw on a gloss coat and starting playing with the oils. On the right is the oiled motor, but no drybrushing quite yet. The little rust speck came out allright.
Do or die at this point in the game.

Questions about this model:
1. what are the big rivet-like things on the wings in picture 2?
2. what's that little piece in the middle of the corner in picture 3?
3. what is the piece between the engines with the little vents in picture 8?
4. what is the grooved part coming toward you in picture 9?

I appreciate the help; it will enable me to make better choices about the weathering.