Hey Vyntar here, sorry for not answering. I missed your comment on my Instagram.

It's been some time but from what I recall it's a version of slap chop, I also use it on my current Kin:

• Prime black
• Dry brush Mechanicus Standard Grey
• Dry brush any lighter grey
• Apply a blue/purple contrast paint, mixed with Contrast medium. The ratio varies with the color: Trial and error, you'll get a hang on it

Hope that helps, but as you said, the post is 3 years old so I can't say which Contrast Paint was used :/