Read somewhere that coal gives you a hotter fire in a smaller spot, which helps with certain welds, so it might not just be nostalgia. Gas is way easier to control though, and I'd bet most guys making billets these days run gas. Your mentor probably learned on coal because that's all there was.

Oh man that ratio is brutal lol. You basically did a whole workout for a dozen people. Next time just tape the flyer to a pizza box and call it a day.

Stone works but steel preheats way faster for me.