"According to a variety of surveys, an individual's greatest fear is public speaking. The next biggest is death. Does that sound true? That means to the average person, if you show up at a funeral, you're better off showing up dead than delivering the eulogy." John Steinbeck, Writer
If you are writing or speaking in public, successful communication starts and ends with the what -- the content. The how will come easier. If writing training and presentation skills training help you in gaining confidence (and you will have confidence because you'll be an expert) you'll have no worries writing or speaking in public.
To get there, aided by writing skills training, keep in mind the three foundations of effective business communication, written or spoken:
Writing is thinking. Compared to a spontaneous conversation, writing -- whether a presentation at a meeting or a report for the boss or a sales pitch -- gives you the time to show how smart you are.
Understand your audience and your readers. How much do they know already? Are they specialists? Do they want to be amused or informed or persuaded? What do you want them to get from your speech?
Study and revise and, when delivering presentation skills training, practice time and again. If you don't check your work carefully before sending it, or practice the details and delivery of your presentation, you risk looking careless and unprofessional. It's called quality control, without which successful communication is nearly impossible.