argon is slightly more expensive than Nitro and is heavier than air/nitro.
100% correct
Inert gas is my method.
Nitrogen and argon are equally effective. There is no odor difference.
Important point is to make sure the gas you buy is not mixed with any other gas. 99% pure is ok.
You need 600 liters = 22 cuft. to finish the job properly.
Industrial gas tanks only come in size of 20, 40, 60, 80 cuft
So you will need a 40 cuft size to guarantee ctb.
Extra is good for trial runs, without compromising the needed amount.
If in USA, here is a supplier who will ship full tanks of N2 to lower 48 via UPS ground:
https://weldingsupply.com/cgi-bin/einstein.pl?PNUM::1:UNDEF:X:40CYL-N