Photoshop next for all of the texturing. I've really gone to town with up to a hundred different maps. All of the careful labelling pays off here so I can keep track of all the maps. They're all 4K too. I've learnt from print that you can always res-down at a later date but you can't res-up! The image here is the colour or diffuse map for the heat vents around the gun barrel with the UV map laid out on top.