Modify the 3D Print
For my purposes, the 3D print needed to be modified. I removed the ridge around the eye using a dremel tool with a sanding bit.
I also thought the body was too short and it needed a head fin. I cut the tail off of my test print - luckily the sizing worked out perfectly. I also used one of the pectoral (side) fins from the test model as a dorsal (top) fin.
I painted the inside of the mouth red, and then started building with Magic Sculpt - a two part epoxy sculpting putty that when combined has a chemical reaction and dries very hard. Interesting fact: this putty is often used by taxidermists to build up muscle structures on animals.
I used Magic Sculpt to build teeth, flesh out the head, attach the dorsal fin, and round out the bottom of the skeleton (it sat flat on the table previously).