I came from a Skaven perspective before moving to Lizardmen. For my Skaven I often used a unit of 9 Gutter Runners with poison slings (2xmulti shot, poison, bs4, skirmishers, scouts) hey doesn't that look familiar? Same as chameleon skinks. The reason i use 9 is I often am only taking 1 unit of chameleon skinks and I want to maximize my chance of taking out a warmachine. Generally warmachines have 3 wounds. 18 poison shots hitting on 6s should net you 3 6s on average dice.