I dunno, Andy. I've never seen anyone do serious smithing with charcoal except youtube videos of japanese sword makers (and they are using mountains!). As I believe I've said, it's an interesting and rewarding fuel to use, and one I have used a lot, but it has vey serious limitations. I like to work mild steel at almost a dripping heat, which is just not possible using charcoal. Welding anything over about 16mm is also going to be a problem just from the sheer volume of fuel you will need. And doing anything resembling a production run becomes a problem because the charcoal gets pushed about, and the heat dissipates while the charcoal that you don't want to be on fire burns merrily away. "Fire flies" have nothing to do with it.