I have been teaching and repairing voices for many years now. I have taught actors, professional media personnel, voice-over speakers, fitness instructors, and, of course, singers of all calibers. To survive in those described above professions, you need a strong voice, a voice which will never let down its user.
The voice is our main tool for communication.
The first thing to do is to fix the speaking voice (this applies to both speakers and singers); and then teach both (a speaker and a singer) how to apply a new technique for their speaking voice.
Then, respectively, teach a singer how to sing a new way – not pushing the sound of their voice down to their throat by virtue of dropping the jaw almost down to the knee, and also not simultaneously sticking the stomach out and pelvis forward.