Without being too wordy, it would be wise to suggest that moms should pray and seek patience through the Lord for anger issues.
First, Michelle never said that using a soft voice will solve the problem. She basically said that practicing and getting into the habit of a soft answer (which the Bible says) is the way to calm herself before applying discipline. Sometimes it may help to have the child go and sit somewhere while the mom gets a handle on her own emotions. Then the discipline can be applied appropriately. This is NOT easy and requires alot of practice, and we all get practice opportunities.
Michelle teaches during school time certain bible passages for character training, including resolving sibling squabbles. For the older ones, she encourages them to apply these principles in their own lives. In the book she gives an example of her kids’ argument and how to show them to handle it. After doing this, she expects them to work out future arguments on their own, and if it’s brought to mom, it will be no fun. 🙂
I encourage those interested to buy or find the book via library. The Duggars go into more details. Although I don’t do everything the way Michelle does, it is good to find nuggets of God’s wisdom that personally speak to me.
Hope this helps!