Might as well tag this in case people want to see the recipe #warhammer40k #paintingwarhammer
Astrogranite is good for that! I like to heighten the effect it gives with deeper cuts as well. There's a lot you can do if how crazy you wanna go with it like I did. Here's an older base I did for a Gorkanaut a that shows the end results. I wrote a recipe in the alt text.