gas tank sodering

Rani unless you are CERTAIN that you take good precautions, this might not end well.

Obviously the safest way would be to have the tank repaired by a pro, like a radiator guy who has and will do so

Otherwise, the safest would be to pull the tank and fill nearly full of water, leaving just a small cavity where you need to make the repair.

When I installed the return fitting in my car, I did this..................

Drained, emptied the tank. Pulled the vent line loose up in the filler neck and extended it out away from the car

With no other outlets except the open cap, I plumbed the CO2 into the outlet on the sender and ran CO2 for several minutes. Used the CO2 / regulator right off the MIG

When "I figgured" it was about flooded, I installed the fuel cap and LIT the vent line fumes at the extension away from the car. When the flame went out I knew I was close, and "gave" it about another 2 minutes worth of CO2, leaving it flow while brazing.