Paining a Child for Chinuch

There are many sources which indicate that at times a light hit is warranted to properly fulfill the mitzvah of chinuch habonim.
But it is important to note the numerous potential pitfalls in fulfilling this complex mitzvah. The Sefer Habris explains that one who hits his child too hard, or pains him for no reason, violates both positive and negative Torah commandments.
In addition, the Shulchan Aruch HaRav rules that one may not strike a child unless he does so to give moral direction. With any other intention—like when striking a stranger’s child—it is forbidden since this is not for the child's benefit.
When Rav Chaim Kanievsky, shlit”a, was asked if one should hit nowadays, he replied, “You certainly must hit, but only at very rare intervals. If a child does a very serious action this is appropriate as the verse states clearly, 'חושך שבטו שונא בנו'—‘One who spares his rod hates his child.’ Yet one may only hit with great discretion and understanding, since one who foolishly hits every day renders this punishment completely ineffectual and pointless.”
Rav Aryeh Carmel, zt”l, once asked his Rebbe, Rav Dessler, zt”l, "Physiologists say that hitting breaks a child’s self-confidence, since his parent acts like his enemy if only for an instant. In addition, surely many people are prone to hit out of anger and not really to help their child?”
Rav Dessler replied to both claims. “As far as hitting in anger, this is absolutely forbidden, so it is not a consideration. A ‘baal middos’ or even someone who follows halachah never hits his child out of anger. As far as breaking a child’s self confidence, perhaps the very minimal amount of erosion as a result of proper hitting is the best thing for the child, since his feeling of absolute confidence is actually negative. If he feels that he knows best, how will he receive from his parents or teachers? In addition, too much self-assurance is one of the main reasons people reject Torah.
He concluded, “We must also consider that our desire to avoid hitting a child in any circumstance as a result of our great love for him may be a violation of 'חושך שבטו שונא בנו'. Perhaps our desire that the child have an overinflated self-confidence is the opposite of what is truly best for the child!”
But Rav Wolbe, zt"l, held that potching a child is virtually never advisable. "Although the verse states,'חושך שבטו שונא בנו'—‘One who spares his rod hates his child,’ this need not be taken literally.After all, what a parent says or even a sharp look can sometimes sting like a blow and is sufficient for one who educates properly."