pitch & resonance tips:
try saying something at exactly
this pitch (average female voice pitch A3 - 220hz). Then try saying it "around" that pitch. Going up and down in pitch over the course of a sentence / word helps.
And yes, moving your adams apple up such as when you swallow is where it should be for better resonance, but don't force it up with your fingers no no no.
I tend to touch it, swallow, feel it go up there, keep it up and relax other muscles, and then keep touching it as I talk to practice. Anymore, I don't have to keep my finger there, it has become muscle memory. Makes such an amazing difference to be able to hear the resonance change! Very exciting!
Good luck! You'll get it! It takes a LOT of practice though. I practice in the car every day to and from work. It's been 2 months since I started and I finally JUST recently feel like I've been getting somewhere. I still have a hard time actually using it in public though, need to build up some experiential confidence

Listening to GG's is the best tip of all. The difference in the pronunciation of S's is huge.