No specific upgrade for the shoulders.
There is 2 parts, shoulders and shoulders thrusters.
Shoulders receive usual paiting Dark grey and will be brushed with Steel Metallic color.
Same paint work as the jetpack thrusters for the shoulders thrusters. I made a sort of blue fuel tank with a yellow line. I don’t make a real fuel tank like for the jetpack, putting putty inside holes, the holes there are made to put in place the armor, they are essential so you need to let them empty.
As I don’t have yellow pen, I made the yellow line with some very diluted yellow paint.
Applying that with a thin brush make the diluted paint fit all along the line capillary way.
I put the exhaust on each plots, made the details with silver ink and lines with black pen.
There’s the result ^_^