I've tried using a two torch method mostly to bring up the temp of larger pieces, using a sievert (I've a few different nozzels for this and it's a case of working out the best) and my Dremel Versaflame.

I either have the pieces pinned with T pins on the charcoal block with the torches coming in from either side or on a mesh on a tripod (although the steel mesh soaks away some of the heat). Problem is that I'm in an unheated garage and in the cold we had the Dremel had a teensy weensy flame and took a while for the stored gas to warm up and he flame to grow to a usable length. It was a bit like Ghostbusters not letting the streams cross.

Still playing with it to work out how to do it right. I've hardly melted any of the 3mm bezels I'm doing on my old penny conchos.