[Brett] from [Theoretically Practical] has done with his old MIG welder ... before energizing the filler wire, while post-flow keeps the gas going after the weld is complete.

[Dominik Meffert] has done exactly this with his wire 3D printer project. Extruder cold end using a standard feeder roller For his filament, [Dominik] chose standard welding wire, and has also ...