My personal approach to painting Old World Night Goblins to create a vivid old-school look.
Heavy dry brush of Eshin Grey and Dawnstone. Light highlights on raised areas using Celestra Grey over the Nuln Oil Shade for contrast. A second Nuln Oil Shade should be added over the Celestra Grey to further enhance the depth. This step should also be repeated for Shaman and Warboss robes as well on any banners for Standard Bearers.
A simple approach that creates a high-contrast metallic effect, base coating all parts in Leadbelcher with a generous wash of Nuln Oil. Drybrushing with Necron Compound creates striking edge highlights and a shortened look on any raise areas There is also the opportunity to use Hashut Copper to dry brush in some rusted detail selectively.
(Optional step: add blood splatter effects across the blades of weapons and armour spending on desired appearance).
To achieve a somewhat authentic Fly Agaric appearance, the whole mushroom should be coated in Palid Wych Flesh, with Grax Earthshade applied to the stalk and recesses. The top portion of the mushroom should then be Layered with Wazdakka Red and edge highlighted with Evil Sunz Scarlett. Palid Wych Flesh can also be used to add the characteristic white spots.