Nothing exploded but I learned my lessons the hard way. I used to do MC painting as a side line and oddly the tank was always dented!! I had one shoot 2-3' of flame out of the cap hole while sounding like a jet engine for what seemed like an hour while heating a dent with a torch, but was probably 2 or 3 seconds, it blew itself out. Stunned silence followed.
I air dry, solvent rinse, acetone or lacquer thinner rinse and air dry again. Gas is trapped, absorbed in the varnish, until ALL the varnish is gone you are handling a bomb. if your compressed air is dry you have the risk of a spark while drying. Water rinse is a fools game unless you leave the tank filled. I have had no luck welding metal that was backed by water.... Yes buy a welder any welder and practice. The night school class is good lets you mess with all the different techniques.
In typical gggGary style, I have a gas MIG, oxy acetylene torch, and 2 tigs, a smaller but still transformer based Miller square wave, and Chinese scratch start "suitcase" that works quite well for steel, My quick go to is still the MIG But I messed with the TIG a few times and would go that way or gas when I finally get to a major build. I'm still looking for a good torch with brazing welding tips for the oxy acetylene set.