Torch Firing Promethius Bronze Clay

Hi Guys,
I’m new to this and New to firing metal clay! After speaking to Cookson today they said you guys were the best so here goes.

I am trying to torch fire Promethius bronze/ light Bronze metal clay. I’ve have tried everything but to no success. At the most I have ended up with a small slither of bronze but most of the time it’s a just crumbly black mess. I’ve been through 200 gs already.
I started with a small torch and then upgraded to something more powerful as I thought the temp was too low. I burn the binders successfully then try and keep it at a cherry red glow. I’ve used different sizes clay but most of the time a rectangle piece about 2 inch 1 inch, which is air dried for over 24 hours.
I’ve tried firing for anything from 5 minutes to 15 minutes, I’m using a firing brick and dropping it straight into water after then attempting to scratch off the black...which always just crumbles.

I understand a kiln is more successful but the instructions and YouTube show it’s possible.
Your help would be really appreciated as I really don’t want to give up!
Thanks