This is a written version of the Sonic Sledgehammer tutorial. Not my work, just lightly adapted to my paints.

1. Undercoat in Matt Black Undercoat .

Armor drybrush

https://www.youtube.com/watch?v=haAZ3mXTrpU&t=2m05s

1. Paint the metal shoulder and leg armor as well as the backpack with Corvus Black .
2. Drybrush armor edges with Etherium Blue (or another light grey like Ulthuan Grey ). Restore chalky flat areas with Corvus Black .

Robes drybrush

https://www.youtube.com/watch?v=haAZ3mXTrpU&t=6m37s

1. Paint the inside of the robes with Gal Vorbak Red (or Khorne Red ).
2. Paint outside of the robes with Mephiston Red . Avoid armor (inside of robes you can just clean up).
3. Drybrush edges and raised parts of the robes with Lugganath Orange , first the outside then very lightly the insides.
4. Shade the inside and outside of the robes with Carroburg Crimson . Ensure it doesn't pool too much.

Head & white elements

https://www.youtube.com/watch?v=haAZ3mXTrpU&t=12m05s

1. Paint white wings, fleur-de-lis, hair and face with Ulthuan Grey (or Corax White or White Scar ). Use multiple coats to ensure coverage.

Gun & equipment

https://www.youtube.com/watch?v=haAZ3mXTrpU&t=12m58s

1. Paint leather straps, gloves and bags with Dryad Bark or Rhinox Hide .
2. Paint gun with Leadbelcher and highlight studs on gloves, armor and backpack.

Black shading

1. Shade everything except for the robes in Nuln Oil .

Head

https://www.youtube.com/watch?v=haAZ3mXTrpU&t=15m10s

1. Drybrush Praxeti White on the hair and white shoulder pad (careful to not hit anything else).
2. Paint face with Guilliman Flesh .

Highlights

1. Paint gold detail with Retributor Armour (or Liberator Gold ).
2. Shade upper gun barrel section with Agrax Earthshade .
3. Add decal.
4. Drybrush outside of the robes with Lugganath Orange again lightly.
5. Varnish with Anti-Shine Matt Varnish .