A combination of the video linked (for all the detail work), with the 'Armour of the Dark Gods' video by Duncan Rhoades for the metallic Tzeentch armour.

1. Prime Chaos Black

Main metallic armour (https://www.youtube.com/watch?v=UDvri5Aa1m8)

1. Cover all the armour pieces, not the armour trim however, with two thin coats of Stormhost Silver
2. Cover all the silver with Gryph-charger Grey , try to apply it evenly, as it will serve as a base texture for the other contrasts to stick to.
3. Now take Akhelian Green and thin it with a little bit of water, and do the same with Terradon Turquoise . Cover the armour one panel at a time by colouring it in with the Akhelian Green with some tiny splashes of Terradon Turquoise for the variety.
4. Pick out all of the armour trim with Retributor Armour
5. Liberator Gold
6. Mephiston Red
7. Leadbelcher
8. Abaddon Black
9. White Scar
10. Drakenhof Nightshade
11. Reikland Fleshshade
12. Druchii Violet replace with Carroburg Crimson
13. Nuln Oil
14. Averland Sunset
15. Warp Lightning replace with Hexwraith Flame
16. Apothecary White replace with White Scar
17. https://www.youtube.com/watch?v=UDvri5Aa1m8
18. https://www.youtube.com/watch?v=pIqHATHsll0