Habit training seems daunting, so simple and yet so elusive in implementation. I claim no expertise, but I do know a few truths about habit training.
You must choose one problem area--just one! Focus on it like a laser.
Write it down so you don't get distracted and so you can keep track of what you've already worked on.
Name the complementary good habit you'll be developing.
Pray over it with your spouse.
Read about effective interventions.
Find appropriate scripture to meditate on and perhaps to share with your dc (but carefully).
Find good stories illustrating the contrary good habit in action if you can, but do not overemphasize the moral. Let the story mostly speak for itself. Also, avoid twaddly moral stories. The story should be good in and of itself, not a story designed just to illustrate a moral.
Intervene gently, preferably BEFORE the problem occurs. This requires vigilance.
Practice the positive behavior that will replace the negative one--make it fun!
When the negative behavior occurs, have a do-over. Be patient and allow your dc to agree to try again.
Keep everything positive!
Stick with it for at least six weeks, just working on this one thing.