Back in the eighties, I scored 45 gal. drum of w/w's, before zinc was invented. They were all melted in my RCBS furnace, which looks like hell, but is still going strong.
It took too long to pour through the nozzle, so I simply picked up the furnace with welders mitts, and poured the lead over the side. It blistered the paint on that side, but there's not much paint left there anyway.
When your bullets are coming out dirty, it's time to clean the pot. Dump out the lead, and after the pot has cooled, pour boiling water into it. Most of the salts and lead oxides are water soluble and will dissolve in the water. After about ten minutes, dump out the water, and the leaded goop that is left, is easily scraped off with a screwdriver. DON'T use a steel brush in a power drill to loosen up the crud. That raises a lot of lead dust which is easily inhaled.