@nerthos with flux core i find that the cleaning action of the flux combined with the arc consuming the filler helps immensely with residue and junk that can't easily be cleaned away even with sanding and solvent (i always do my best to clean to bare metal but you know sometimes there is stuff buried, or coatings on the inside of pipes and so on)
whereas with tig, for example, any little bit of of zinc residue causes a mini explosion which ruins your electrode instantly
the other day i had to grind back some epoxy primer used tig to fix something i missed, and it actually worked out fine though.