It was quite easy actually. I used P3 Gnarls Green and gave it a heavy highlight with p3 Wyrm Green. It looked quite toxic and had a huge contrast. Then I washed it all with the OOP green GW wash, I guess another brand or their new version would be fine too. Just to blend the colours and tone down the toxic Wyrm Green.
After that I painted eyes, swords, teeth etc and corrected errors.