I can't get too upset about smacking. Punishment is meant to be unpleasant
My Dad exclusively smacked. We'd do something that displeased him, he'd smack or fling a slipper and that would be it. Don't do it again and back to normal.
My Mother, on the other hand, would use from a very early age in order of preference:
Ignoring (shut in room for hours then ignored for days)
Withholding affection ("Have I been good enough today? Do you love me?")
Smacking (rarely but full on, hysterical slapping and shrieking)
I wasn't a dreadful child, I don't think, and can count on a thumb and a finger the number of times I was told off at school.
The problem was never the form of punishment but the fact that whenever my mother punished it was to excess, and in that moment, she absolutely HATED me. Also that my brother was not held to the same standards (he has ASD but knew full well what was expected).
I know a lot of posters won't agree but to me, it's about the fact you understand you've behaved badly but you'll do better next time and your parent still loves you. I'd never advocate using implements or leaving marks.
I have no children and no intention to, in case anyone is worried.