The Iron Warriors were the seige specialists.
They had alot of MK3 armor for the superior frontal armor.
I like to model them as down and dirty trench fighters
The Iron Warriors Upgrade was used to make this model with a simple shortening of a melta-gun to make it compact
I primed it black because metallics look better over black

1)-Boltgun Metal for the armor plate,
-Shining Gold for the Trim
-Tau-Sept Ochre for any yellow
-I then gave a thinned wash of Badab Black wash

2)-2 coats Undiluted Badab Black wash,letting each coat dry fully before adding the next
-1st layer an undiluted 50/50 mix of Asurmen black and Badab Black

3)-Highlight the armor plate with Boltgun Metal
-Paint the yellows areas Iyanden Darksun and the stripes Chaos Black
-Give the armor another wash of Asurmen Blue/Badab Black

4)-Neaten up any stripes
-Shade Yellow with a few layers Delivn Mud wash
-Give the Gold Trim a wash of Devlin Mud

5)-Using Mithril Silver paint an outline of a skull

6)-Using a mix of Boltgun Metal and Chaos Black paith the eyes and lines for the mouth

7)-1 layer of Devlin Brown wash on the legs below the knees
-1 layer of watered down Graveyard Earth
-Devin Brown wash spoltched over the graveyard earth
-The end of the melta I used Scorched Brown and Chaos Black
-The old codex would let you use servo-arms I like to model them on mine