This is basically the same method I used to train my voice just with different information to get there. Sadly I can't find the link to the material I used...
For a month or two, I didn't actually say a great deal, instead just focusing on controlling those muscles. It's what gives you absolute control over your voice, and I'd say it's easily the most important part in mtf voice training. And like any muscle, you need to keep using it for it to stay strong and under control. Every morning I still need to 'stretch' my vocal muscles for a few minutes.
I may also note, if you do get your voice into the correct shape, it's impossible ( at least for me ) to sound male. That was a huge shock!

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There's also much more which goes on top of it, learning to control head resonance, timbre, twang. But you can worry about those later.
P.S. It's not a shortcut. It'll still take a minimum of many months to start sounding like a girl.