Youtuber bluworm has a great process video showing how he made a latex octopus for a stop-motion film. I found this via the Craft Magazine blog, which reposted it from Sean Michael Ragan at the Make Magazine blog. He found it via Propnomicon, which finally led me to the website and blog of Tom Banwell, who makes quite the array of projects in leather and resin, many with a steampunk flair.