Here is another shot of how the pitch bowl works well with irregular parts for a pistol. I am cleaning up a side plate and monster head. Both irregular objects which could be marred or difficult to hold. The pitch holds it whithout any movement and you can bang arround and scrape as much as you want. To get it out all you have to do us use a blunt tool (screw driver) just next to the item and hit the pitch which will shatter and release the object. Any pitch left on the object can be wiped off with denatured alcohol.
To place an object you need to just think of how big the item is, heat the pitch with a torch or heat gun and using cold metal tools move the heated pitch into a mound. Once it is the right hight heat the metal object and put it in place and use a cold metal object (like a hammer head) to push the pitch arround it.
Pitch mixture is called matsuyani and is made of mixing 1 Kg finely ground fire clay or Plaster of Paris, 750 grams of Pine Rosin, 50 ml of vegetable oil, 1 teaspoon of charcoal powder. That recipie is from Ford Hallam.
You can get steel hemispheres for about $40 or so and the above mixture will cost you about $30-50. So its also much cheaper than a jewlers ball vise which run about $300.
The rope donut is nothing more than three turns of 1/2 inch manila sewn together and bound with stout cloth and with a bit of beeswax smeared on the top to give it just a bit of stickyness.
You can turn your bowl and tilt it however you like.