The lighter colors (skeleton bone, stone golem and corpse pale) are darkened more by the wash than the darker colors, that's why i use the same color for highlighting those lighter colors instead of using a lighter highlighting color as i do for the darker colors.
Preparation step two is to saturate the base texture with it's high surface area, which can be messy and spill on an already painted miniature. The small amount of black spill on the base in step 3 will be easily fixed in basecoating step one without having to paint the entire base.

Preparation

1. Lightly prime with Matt Black Undercoat or airbrush
2. Paint textured base with Uniform Grey or Neutral Grey
3. Paint everywhere you didn't reach or cover with spraying Matt Black , try to get as little as possible on the base, but be sure to cover the feet
4. Zenithal highlight with Uniform Grey or Neutral Grey
5. Airbrush dot highlights on rounded parts (helmet, shoulder pads, power pack exhausts, kneecaps, calves, boot caps) with Uniform Grey or Neutral Grey

Basecoating

1. Paint weapons and base with Uniform Grey or Neutral Grey
2. Paint chains, barrels, blades, grenades, etc with Gun Metal
3. Paint heraldics (aquilla, skulls, etc) with Stone Golem , this will take two to three coats to cover.
4. Paint parchment and ruin details on the base with Skeleton Bone , this will take two coats to cover.
5. Paint lenses, wax seals, (and right shoulder trim for 3rd company) Dragon Red , this will take two coats to cover.
6. Paint plasma, energy details (chainsword) and some lenses (scopes) with Ultramarine Blue
7. Paint Binocular lenses with Greenskin
8. Paint skin with Corpse Pale , this will take at least three coats to cover.

Fix mistakes

1. To match the armor color, put a drop of Black and Neutral Grey next to each other and mix a gradient between them.
2. Use the respective colors to fix all of the little spills and mistakes and paint the hair Black

Wash

1. Wash all over with Agrax Earthshade

Highlighting

1. Highlight skin with Corpse Pale , repeat washing with Agrax Earthshade and highlighting multiple times to get some layering and to get the eyes dark
2. Highlight green lenses with another layer of Greenskin , then Goblin Green and a dot of Matt White
3. Highlight blue parts with another layer of Ultramarine Blue , then Crystal Blue and a dot of Matt White (put the white dot on the darkest blue on lenses)
4. Highlight lenses, wax seals and red trim with Pure Red
5. Highlight parchment and ruin details on the base with Skeleton Bone , then add writing with Matt Black
6. Highlight heraldics with Stone Golem
7. Highlight metallic parts with Plate Mail Metal
8. Highlight weapons and drybrush grey base texture with Ash Grey
9. Highlight armor with Uniform Grey or Neutral Grey . Since this is the most demanding step and most easy to mess up, I decided to skip it on some of my troops. Here I only highlighted parts I felt confident not to mess up.
10. Finally, paint the rim of the base Black

Done

1. And
2. We
3. Are
4. Done