Milliput is a two-part epoxy putty with a long record in model and restoration work, and it is known for two things. It can be smoothed with a wet finger or a wet tool while still soft, which lets you blend a repair into the surrounding surface without any sanding at all. And once cured it is genuinely hard — hard enough to drill, tap a thread into, file and polish, with no shrinkage as it sets.
Mix equal parts until the colour is completely uniform, work with wet tools, and expect a working window of roughly an hour or two depending on temperature. A finer grade sands to a smoother finish and suits visible repairs; coarser grades are easier to build up in bulk. Compare working times and grain across the other options in epoxy putty, and keep silicone shapers and steel sculpting tools to hand for shaping before it firms up.
