You can definitely use systematic desensitization -- that's probably the best strategy for overcoming fear of public speaking. This is exactly how Toastmasters works. I highly recommend you find a club in your area (there's a club locator at
Welcome to Toastmasters International where we are"Making Effective Communication a Worldwide Reality") and attend a meeting as a guest.
You won't be required to speak as a guest, but after you join, your first speech is a 4-6 minute icebreaker. From there you work through a manual of 10 speeches, mostly 5-7 minutes each. Each speech project focuses on developed specific skills like speech organization, gesturing, vocal variety, etc. A big part of overcoming fear is learning to be a competent speaker. You'll learn how to write and deliver better presentations.
I've been in Toastmasters for 3 years now and still get a lot out of it. Some people join several clubs, so they can speak more often and go to more meetings.