One of the more daunting tasks when making dice is finishing them. I remember when I first started making dice, I had absolutely no idea how to properly sand them, polish them, and make them look nice. It took a few months to really find my groove on not just what to use, but how to use it.
Things you'll need:
-1500 or 2000 grit wet or dry sanding paper
-Water in a small bowl
-Nitrile gloves
-A smooth, waterproof surface
-Patience
Step One:
Put on a good podcast. I recommend Critical Role Campaign 2, since you can both watch if you'd like, or listen. You'll want something interesting, as sometimes finishing dice can be time consuming. On your smooth, waterproof surface (I know several people who use the glass out of a picture frame, but when I sand at home I do it right on my granite counter), lay down your 1500 or 2000 grit sandpaper and drip a small puddle in the middle. Locate which side of the die the sprue mark is on. Lightly, and picking up your die every few seconds to check, lay a face of the die that needs to be sanded flat and parallel to the surface on the sanding paper and sand in a small, circular motion. Check every couple circles to see the progress you're making on getting most of the sprue even and level with the rest of the face of the die.
You want to use the 1500/2000 sand paper to get the most of the sprue off in an effort to preserve your Zona papers. Once you're happy with how your 1500/2000 grit sanding has the sprue looking, your next step will be using those Zona papers.
Step 2:
Zona papers are magic. Truly. You'll really start to see the polishing effect starting on the pink paper. You'll want to cut a 2" x 2" square and thoroughly wet it down so it sticks to your smooth surface. Using small circles, just like you did on the 1500/2000 sandpaper, you'll want to sand each face of the die the sprue is on. There's no perfect count or amount of times sanding with each color of Zona, but a good rule of thumb is to make sure you're not seeing the sanding marks from the previous level of Zona. If you move to a different color and are still seeing scratches when you check the face of the die, go back down a level and sand a bit more.
Step 3:
Once I've gone through all the levels of Zona, I like to take my finished dice and give them a nice bath in warm water with a drop or two of Dawn dish soap, using a toothbrush to get the sanding gunk out of the numbers. As for inking, I really recommend fine tip paint pens. They make quick work of those tiny numbers!