I recently worked on metal material for animation. The model is 2.6 Million polygons (amazing model from Ludovic Gicqueau!) The animation is 1400 frames 1280x840. I want my render to be quite fast (around 1 minute/frame) so I had to find some good tips to speed up rendering. I have first tried the "environment blur" hidden shader from Zap but It only works fine with Final Gather. My basic setting is an Ambiant Occlusion Light shader on an omni light (aligned and linked to the camera). No light on in the scene, the mental light shader works with light off too. HDRI in the enviroment for far reflections and reduced reflection max distance. No Fg, no GI.