Prosthetics for fun for halloween etc are quick and easy to make from gelatine. We made some severed fngers in class one day and they were soo realistic, the coloration is key when trying to make a realistic severed finger.
This is done by casting your finger (or whatever body part you wish!) using LIFE FORM a two part formula made from silicone.
This is slathered upon your chosen body part allowed to set or ”go off” and then filled with melted gelatine. When this sets simply remove it from the silicone and powder down before painting it with some alcohol activated paints.