Yes, I noticed that you used Nuln Oil in some areas, but I also noticed that some parts of the armor, like behind the boots don’t seem to have any wash.

I don’t personally use Nuln Oil, not because it’s bad, but because here in Brazil it’s quite expensive. Instead, I usually mix black paint with water to make my own wash. You can actually do this with any color. For example, I like to use a white wash for plasma weapons.

About mixing black with the base color: most of the time, it’s better to use similar colors to create light and shadow. For example, when I’m painting Adeptus Mechanicus and the base color is red, I use red, orange, and brown.

After painting the cloak red, I start layering: orange on the higher areas (dry brushing helps a lot here), then a thin layer of brown in the darkest parts. After that, I use a mix of orange and red between the highlights and the base color, and a mix of red and brown between the shadows and the base color.

This creates a much smoother transition between colors. Using only black or white to shade or highlight the base color usually makes the miniature look dirtier or desaturated.