Once dry, I waxed and burnished it using these instructions. I liked how lo-fi this process was and how much it emulates natural erosion process. The final finish is almost matte, with a low, satin sheen.
Rather than trying to smooth out the top surface, perhaps next time I'll be more intentional about the irregularity. Omar Abel's bronze bowls are a great precedent of exploiting the irregularities of a material and process.