I'm designing my own MIG welding torch that uses consumable from commercially available MIG guns
MIG (Metal Inert Gas) Welding uses a a spool of steel wire that feeds out of the torch like a hot-glue gun when welding. The weld puddle is protected by carbon dioxide or argon which flows out of the nozzle at the same time.
MIG is the fastest manual welding process and also the easiest to learn.