Remove the sink, stove and whatever else is going to be in the way. Also tape off the areas where you don’t want paint, like the backsplash (which we haven’t installed yet).
Prime the countertop. I didn’t do this, I just went straight into painting. Swim at your own risk. If you choose to prime I would recommend an oil based primer,
Paint the countertop. On a large surface using a small roller would be ideal, but my surface was tiny and had lots of cutouts, so I just used a paintbrush.