Just wow - thanks to everyone checking it out, way cool.
He was rendered really big, 12000 pixels wide (greyscale) and the surfaces were very smooth to begin with (no pipes or damage). The detail is Photoshop but having these huge shapes correctly lit to play with makes it easier cuz shrinking it down creates a lot of the detail.
Used the brush tool and its blend modes to paint onto the render, building up it up in colour then the lil stuff. Few bits of rust and metal texture clone tooled in. Lots of 1px brush work, lots of patience hehe. Worked on it for a couple weeks with some other stuff, not solid tho.
very unique and original in terms of mechs