I have taught myself tig over the last 4/5 years for our custom frames. Tig welding to pieces together is not difficult, doing it neatly (and on thin wll bike tube) is not so easy. All the recomendations I had for learngin (from Sheffield uni, other framebuilders and fabricators) was to cut up loads of pieces similar to what you will be using and just go at it, and keep going until you get better. It really is a case of practice makes perfect. If you can make a project as you go then great.
this is about 1% of my learning pieces. It was much thicker wall but gave me a great start. We still have loads of that tubing left if you want, you can have it for free, but you’ll have to come and get it ; )
Once you start getting better, try to remember what you were doing different on that pass and concentrate on recreating it. I would recommend using a foot pedal if your planning any slightly thin wall stuff although i have never used a torch switch type set up.
The main hint I can give ( and people will think I’m taking the mick but I’m not) is to BREATH. It will make a huge difference. Soon enough you’ll have welds like the one on this page
The advice about backpurging is wise, it makes a big difference, as does stainless filler even on non-stainless but this doesn’t work in all situations.
Wow I can talk about welding!
Matt