Developing the weaker side is always a challenge. Many drummers have a weaker non-dominant hand that lags behind the dominant one. After years of practice both hands improve, but the difference often remains. To reduce it, right-handed drummers need focused work on the left hand, and left-handed drummers need focused work on the right hand.
created an excellent book with many exercises for this purpose. It contains 52 pages, with 30 exercises on each page. The recommended approach is to play each exercise for one minute, so one page takes 30 minutes. Work on each page daily for a week, then move to the next one.
The material can be applied not only to the hands, but also to the feet. You can play the exercises with the hands, with the feet, and with hands and feet together. In this approach, developing the weaker side takes 52 weeks. Of course, the process of improvement never really ends.