Copywriter extraordinaire Jim Logan recently posted the following advice:
Every time you find yourself presenting, speaking, writing, or otherwise communicating with someone and you find yourself saying something like “What I mean by that is…” – stop yourself. Whatever you say afterward is exactly what you should have said in the first place.
The reason this works is that your preface acts as a psychological crutch--because you've already lowered the audience's expectation of eloquence, you're free to say what you mean without feeling the pressure to say it well (which, ironically enough, generally causes people to say things badly).
I even institutionalized this at Symphoniq. Whenever people were struggling to express a complex thought, I asked them to "say it badly" first. Then I'd write down what they said and read it back to them.
More often than not, "saying it badly" resulted in a much better message than any of their previous efforts.
Try this technique for yourself, and let me know how well it works for you!