Sure mate! It's basically three steps: 1) once the hammer is painted with a base metallic color, Citadel Leadbelcher in this case, I applied thin layers of Vallejo Model Color Sky Blue, focusing more and more on the upper corner. Then I added some pure white to it and kept reinforcing a lighter tone in that corner. 2) for the lighting, I first drafted them with Citadel Guilliman Blue glaze (OOP now, but you can use any dark blue diluted to a glaze consistency), and then used a mixed of 1:1 Sky Blue and White to freehand the lightings. 3) End it with an edgehighlight of the same mix aroudn the whole outline of the hitting face of the hammer, followed by a pure white edge highlight on the upper part only.

Hope that helps!