I'm going to paint my first two this weekend. 3D printed models of the Argonath from LOTR. Had them made at a local library and they took 18 hours each!
My plan is to sand a little, then use black automotive primer, then mixtures of gray, "rubber," and army green enamel paints to build up a stone look. Trying to figure out if there is a good way to add weight to them so they might work as bookends for my intended recipient.