I still think there's some merit in that approach. I think J and P functions tend to operate in tandem; therefore a quick fix for a an overactive Dominant function would be to strengthen one's Auxiliary. For example, a Dominant N or S who spends too much time and effort "churning" details in their mind (can't let go of re-hashing scenarios and making plans) could take fairly immediate steps to strengthen their Auxiliary T or F and use it to monitor and cut off excess N/S. And vice versa - strengthen one's Auxiliary N/S to curb close-mindedness of the Dominant T/F (solipsism, getting stuck in one's head) and get quick access to broader interaction with one's environment.
On the other hand, nowadays I'm increasingly a fan of developing one's Inferior (and ideally the Tertiary along with it). It's a longer-term project than working on one's Auxiliary, but the benefits would be bigger as well. The Inferior is the "opposite" of the Dominant and provides a nice complement to it. And the Inferior is the function that we use when we are stressed; therefore getting a handle on "healthy" unstressed application of the Inferior would go a long way toward recognizing and reducing stress.
IOW, developing one's Auxiliary might be a good short-term project for reining in an over-active Dominant; developing one's Inferior would be a long-term project for having a healthier outlook on life as a whole.
In my opinion, of course.