Hexacon electric makes leather brand irons. I currently use a 250w iron. Anything under 100w won't get hit enough. A torch will leave a soot.
I'll use a little acetone to dampen thin 2-3oz leather.
If I use water the leather will curl. I need to get a temperature control and play with the settings.
I also use a fine bristle stainless brush to clean the brass stamp inbetween stamping.