[rotorwrench]

You can buy or rent bottles as a general rule and they generally won't break the bank. Get as large a bottle as you can work with. Straight Argon makes the nice welds but CO2/Argon Mix does OK too. You won't regret using the gas unless you weld outside in the breeze. The gas does no good if the wind blows it away but that's what the flux core is for.

Easy Grind is sort of a trade name. ER70S-6 is available from just about any welding supply. The weld wire with the high numbers makes for a hard joint but its OK if you grind down your welds and don't hammer them too much. The wire has to be hard so as not to break when being fed by a MIG welder system. Too soft a wire will cause feed problems in the small gauges.

The old timers used RG45 rod or bailing wire with their oxy/acetylene rigs so that it would be as soft as you can get. This allows it to be hammered on without work hardening it too much. Those AWS ratings tell you how hard/soft it is and what its made to do. The AWS has a users guide that explains filler metals & electrodes for welding