I've being doing metal casting for a long time, building my own furnaces, burners ... I do mostly aluminum, as it is most often what I need in my projects. Sometimes I do bronze or cast iron, but not too often. I also live in somewhat residential area so I am very conscious about noise and burners can be as loud as small jet engines (injecting fuel under pressure into a small space)
The question about smelting copper and range brass comes from time to time on the metal casting forums. Basically, unless you are developing your own technique, it's not worth it. The smaller are the scraps of metal (i.e. casings) the more is the oxidation. There are ways to minimize it, but you still end-up with lots of dross (oxide waste). It's similar to smelting aluminum cans, there's just very little money to be made. Also, keep in mind that bronze temps require a crucible that you most likely need to buy. You can make them and some guys do, but you got to factor in the risk of it breaking and tens of pounds of molten copper flying everywhere.
Most common flux for copper alloys is Borax and it loves to eat away your expensive cruicibles.
For burners, my guess would be a waste oil fired burner. That's a common way to go and they are fantastic in terms of BTU's. There are a lot of designs, it all depends on what kind of waste oil you are getting, what furnace you have. If you live in the sticks, there may be other options too.
So there are a lot variables. Better knowing the situation, I can give you appropriate advice or point you in the right direction. If you want to go into uncharted territory with some crazy setup, I'd love to participate. In any case, metal casting setup can be a profitable operation since most foundries deal with bigger jobs.