tl;dr for Warhammer's "How to Paint: Space Marine Cloaks" tutorial on youtube.

Undercoat with Mechanicus Standard Grey

Two coats of Blood Angels Red all over cloak

1. https://youtu.be/ZThD7jqyfYE?t=42

Shade all recesses with Flesh Tearers Red mixed with Contrast Medium

1. Mix 5-7 Contrast Medium to 1 Flesh Tearers Red . Apply 3 - 5 **thick** layers or as desired.
2. https://youtu.be/ZThD7jqyfYE?t=92

Shade deep recesses with Basilicanum Grey mixed with Contrast Medium

1. Mix 3 Contrast Medium to 1 Basilicanum Grey . Apply 2-3 layers or as desired.
2. https://youtu.be/ZThD7jqyfYE?t=191

Highlight raised areas with Mephiston Red mixed with Lahmian Medium

1. Mix 3 Lahmian Medium to 1 Mephiston Red . Apply 1 layer(?)
2. https://youtu.be/ZThD7jqyfYE?t=242

Fine highlight raised areas with Wild Rider Red mixed with Lahmian Medium

1. Mix 2 Lahmian Medium to 1 Wild Rider Red . Apply 1 layer(?)
2. https://youtu.be/ZThD7jqyfYE

Line raised areas with Troll Slayer Orange slightly thinned with water

1. https://youtu.be/ZThD7jqyfYE