Certainly writing style is much different from oral style. Word choice, for example, is simpler and more informal in speaking than in writing. But you can learn about oral style by reading. In a recent Wall Street Journal article, movie critic Robert Ebert examined film criticism that is available online. He wrote that due to the rise of technology, companies are able to restore old films so that “Today we can see the work of Buster Keaton more clearly than he could in the last three decades of his life.” The comparison here clarifies the amazing advances in restoration of old films in the minds of the reader.
A comparison can do the same in a speech. The listener cannot go back over what you have said, so you must be instantly clear. The comparison is probably the shortest way to make a point clear.
Ebert contrasted the poor writing styles of academics with the outstanding film criticism now available online: “They communicate in prose as clear as running water.” Again the simple comparison helps the reader understand instantly how Ebert feels about such writing style.
Thus a speaker can learn clarity in his/her craft by reading essays as well as working on specific speaking skills. In fact, any medium other than speaking will broaden our skills in what to say and how to say it.