I personally could never. I'd be too afraid of last-second pulling away as SI kicks in, botching the attempt and either coming our unscathed and humiliated, or worse (and more likely), emerging maimed but not dead. That said, I don't mean to imply it can't be done; many have tried and succeeded. It's just too fearsome for me.
As for pain, if done correctly I imagine it would be painless. But my prediction isn't reliable, I doubt anyone could say definitively how much pain you would experience.