Thanks for the input. I managed to locate a soap recipe that I will try once I've acquired all the ingredients, and of course I will take every precaution before starting. The reason I want to use duck fat is because I had a jar of duck fat that was expired and I didn't want to waste it. Alas, flooding at the location where I was keeping it led to the refrigerator it was stored in being unplugged for nearly a week, and so I had to dump the fat down the drain as it had gone rancid by the time I was able to return to the office to recover it.
But, having used Oleo Soap Works duck-tallow shave soap, I want to try and create my own recipe to see if I can make something similar with my own scent profile (I'm thinking almond with either cherry or vanilla). That, or mutton tallow.