In the telephone industry we melted lead and cast it into plates called disks. Two inches thick and as large in diameter up to 20 inches. Hole were created by placing plugs on the plate within the rings. These were used to join several lead sheathed comm cables together to form an air tight container for splices. We never fluxed just skimmed the dross from the top of the pot until the melt was clean. I stock piled large quantities of this lead and use it today for bullets and balls. Of course those small, large and very large plates weren’t tiny bullets with intricate shapes so matters of filling out the mold and controlled shrinkage hardly mattered. Every cable splicers truck had a complete furnace, shield, pot and disk set along with a 35 pound propane tank, hose and regulator as part of its tool inventory. Sadly those days are mostly gone. Plastic rules the day now.
Today I use commercial fluxing sold by several out lets. A one pound container lasts for years as a small amount is used. I cast in my basement work shop under a hood but still don’t want to deal with the smoke and flare up of the various materials used.