Here is how I paint the unifying weapon colour on my Deathwatch veterans for Kill Team.

1. Basecoat the area with Khorne Red and Abaddon Black , mixed 1:1.
2. Edge highlight everything with a chunky line of Khorne Red .
3. Add a fine highlight of Wazdakka Red to all of the same edges.
4. Highlight corners and exposed edges with Squig Orange brushing towards the centre.
5. Pop specular highlights of Lugganath Orange in the centre of these highlights and on corners.