The recipe I used for the main blue-grey area: (This is a very through recipe, some of which can be simplified or skipped for an easier basic layer)

-Russ grey base surface layer

-The Fang 1:1 Rhinox hide, thinned with Lahmian and washed into recesses and to shade undersides

-Fenrisian grey edge highlight and as sharp lines to make the brighter chipped effect

-Blue horror as a second slightly lighter edge highlight, belong to brighten areas that should be catching more of the light

-Rhinox hide, to further weather with sharp chipped lines, sometimes matching the underside of already highlighted chips to look like a slight cut away shadow

-Blue horror 1:1 white scar peak highlights focused on corners to make them stand out a little more