This, of course, is the heart of the process. But note how many activities occur before the writing. Too often, proposal teams want to jump right into the writing, without really thinking through the other activities. Or, teams wait until the last possible moment to begin the proposal, which means they have to start writing immediately, just to make the deadline. If you follow the process, the writing itself becomes easier because you've been thinking it through as you hit each step.
Reviews are critical to the quality of the proposal.
A final word. Sometimes you simply don't have time to follow each step religiously. In those cases, make sure you have a win strategy, a rough schedule, and a second draft review. Or maybe if you're that short of time, you really shouldn't write the proposal.