As we continue with this rock study, the goal is to add detail. To polish. Starting with the basic block-in from the last video, it's all a matter of close observation. I'll break down large ares of flat gray into smaller pieces of darker gray, and smaller pieces of lighter gray. It's a process of slow sub-dividing, growing ever more specific and detailed.
From a technical standpoint, there's really nothing exciting happening here - it's just a lot of patience and 'temp layers'. Even so, if you're unfamiliar with the techniques make sure to check out the videos linked to the right.