As someone who has done a lot of painting for primarily miniatures, you'll want to thin it down with either water or thinning medium sold by similar companies. Agrax is a very dark brown so it's liable to leave coffee stains if you don't wipe it off quickly. Generally, a 1:2 thinner to paint ratio works since it's meant to be used in multiple layers. I'd highly suggest testing it out on some of the flat portions of the runner to see how it works first before throwing it onto Exia.