I would start with some 3/16 or 1/4" mild steel before the stainless. Stainless does flow better but is more picky about contaminants and type of tungsten.
If you get filler rod in 3' lengths then hold about half way up and just rest the tip on the work piece back a little from the starting point. Get a puddle started without wire then slide it closer to the puddle till it starts to join the puddle. Then just pull back push forward as needed. I would start learning without the pedal and once you get proficient you can introduce the pedal. Much easier that way and to be honest the pedal is only needed in special cases.
Question? How important is it to back gas S.S.?
Back purging is very important if the inner weld surface is important or the weld will sugar without it.
