Do some browsing for ideas, Otzi's people were smelting copper without anything modern. I'd recommend posting for ideas on a knife makers forum, bladeforums helped me out alot. A brake drum forge with a hair dryer might be the way to go and both can be slavaged pretty cheap. There's a guy on youtube that goes by the handle Primitive Technology who's made many a kiln, including manual powered and natural air flows, from completely natural resources, and could be adapted to your needs (ETA turn on the subtitles, he doesn't speak, but narrates through subtitles).