A few things, and I used to speak at a lot of conferences (I am on self imposed exile):
- Get in front of your co-workers with the brief, on a projector. If your organization feels strongly enough to pay you to go speak, they should support the time for you to get pilloried by your co-workers. No tougher crowd. You will learn.
- Toast Masters in your area:
https://napatoastmasters.org/ Do it, you have two months.
Other than those two, go to a Comedy Club. Go watch the real masters. I had a series of briefs to give in San Diego when I was a puppy. Important stuff in my mind. I went to the Comedy Sewer/Cellar/Station with my girlfriend to see Richard Belzer - long time ago.
After his set he was standing by the end of the bar and I decided to ask him how he managed to control the crowd. I was in earnest and he didn't seem surprised at my question...I leaned in, awaiting his response:
"How the **** do I know".
Best advice I have ever gotten concerning public speaking, because, like Dire Straits sang:
Sometimes you're the windshield
Sometimes you're the bug
Sometimes it all comes together baby
Sometimes you're a fool in love
Sometimes you're the louisville slugger
Sometimes you're the ball
Sometimes it all comes together baby
Sometimes you're going to lose it all
Just the way it is.