there are so many ways to do this - (mood swings dictate for me) in this one i did a all grey primary colour then did a white layer, then a shadow layer. I didn’t like the all grey and envisioned your design with a overmolded handle - so i erased the base grey on the handle and filled it back in with blue. that way you don’t really have to redo shadows and highlights (but i did soften them on the blue a little to get a more matt feel)
if you want i can send you the layered tiff file if you provide a email address.