A basic approach for brown skaven.

1. Undercoat with a grey, zenith with a light grey, drybrush with a white.
2. Skin is Guilliman Flesh fur is Gore-grunta Fur armour and metal gets Black Templar cloth is Flesh Tearers Red warpstone is Karandras Green leather is Garaghak's Sewer mouth and tail is Volupus Pink base was done with Basilicanum Grey
3. Metallics are Army Painter Heavy Metal for the silver and Balthasar Gold for the bronze.
4. Wash with Agrax Earthshade or Targor Rageshade
5. Flesh is highlighted with layers of thinned Beige Red for the sores, I thinned some Screamer Pink around the edges and then used the Beige Red in the middle of the sore. Any of the wounds can be edged with Carroburg Crimson to make them look sore.
6. Black Armor is highlighted with First edge highlight is a 2:1 mix of Thunderhawk Blue and Incubi Darkness Second highlight if 1:1 Thunderhawk Blue and Fenrisian Grey
7. The red cloth got a quick highlight with Mephiston Red you could go further with the classic Evil Sunz Scarlet Wild Rider Red triad. While doing the cloth, do some dots for the eyes.