I was under the impression, before seeing this video from intrepid propcaster James Bruton of Xrobots.co.uk, that rotocasting was only practical if you had a machine to automatically spin the mold on multiple axes, simultaneously, for several hours while the casting material sets up. Turns out if you use the right quick-cure resin, it’s practical to rotocast thin hollow shell-type parts just using your hands. The resin is applied in a small number (say 5 or 6) of batches / layers, each of which gels up in a matter of two or three minutes. So all you have to do to cast a helmet, for instance, is mix up a soda-can sized portion of resin, pour it into your helmet mold, and rotate the mold in your hands until the resin covers all the inside surfaces. After that, you just have to keep it from pooling up for 100 seconds or so. Here James is casting legs for his Iron Man MkVI costume.