I don't. It's just not effective, at least not in the long run. And even if it fixed the problem on the surface, it teaches the solving of problems through force, a lesson which I personally picked up on pretty quick as a kid.
I mean I don't consider my parents to have been abusive necessarily, but my step father had this thing he'd do where he would have me go out and pick a branch to be used for a spanking, with the understanding that if I picked one that was too small he'd pick one instead himself. At first it was effective because of the psychological punishment of trying to find a stick that was light enough that it wouldn't hurt too much, but big enough that he wouldn't just choose a bigger one. Eventually, though, I not only became indifferent to the punishment, but learned to use sort of a reverse psychology. I'd find the biggest, nastiest thorn bush I could find rather than looking for something small, which made him mad cause then he'd have to go out and find something smaller lol. Realizing that I no longer feared the punishment, it quickly lost it's appeal.
If only he'd simply used rationalism and logic to explain why what I was doing wrong was wrong, it might have saved us both a lot of frustration and bitterness.
But yeah, I'm never gonna hit my kid.