I've had good fortune with a construction grade tube silicone(100% only), mineral spirit (to thin the silicone), and corn starch (the more you add the faster it'll dry). It can be colored with an oil base or purchased pre colored; mix will vary depending on the balance of the ingredients. Ensure there is proper ventilation (it will have strong vapor smell until cured), start small and add layers until you get the desired effect (mix a little at a time in a disposable container with a sanded thin piece of wood). It can also cover an existing handle as an example see the photo below.
