There are tricks you can use to jump start the writing process - even if your task at hand seems daunting or intimidating. Don't worry about it sounding perfect at this stage.
Revisions can come later.
Write your document the way you would speak it to a business colleague or co-worker. It's a great way to avoid nominalizations that are stuffy, and that cloud your writing. Insert substitute words, or simply a temporary XXX, if you're stuck on one particular word or phrase. Keep moving forward with your business document, and come back to that trouble spot later. Double-space your first draft, leaving yourself plenty of room to make revisions, edits, or notes in the margins.