I rely on PC-11 (white) and PC-7 (grey) for all repair/rebuilding jobs. It's thick and tacky so it can be placed somewhat upright and it will hold its shape. If you don't want a rough surface press Saran wrap or packing tape on the wet surface and peel it off when it dries a day later. If you want something that flows more freely and will fill a mold, use JB Weld instead. All are very strong.