I didn't read "Brutus," only "Orator." I originally started reading "Orator" thinking it was Cicero's "On the Orator," which is a separate book. But after learning they were different, I finished it anyway. This book would be much more beneficial if Latin was my mother tongue, but, as a rhetoric teacher, I still found it edifying as an example of how to teach oratory well. "Orator" does not cover the wide range of rhetorical theory that some of Cicero's other works do. It focuses primarily on style, and rhythm in particular. But what I found edifying was seeing how Cicero teaches rhythm. He doesn't just give some general "rules" to follow but provides many, many examples from famous speeches. Sometimes these examples function as ones to imitate, but many times Cicero actually gives bad examples from famous speeches and corrects them, saying, "As it stands, this arrangement of words doesn't have a nice rhythm. But if he had placed this word here and that word there like this...then this sentence would flow much better." Unfortunately, all of the examples are in Latin.
Cicero also verbalizes some of the problems I have experienced teaching rhetoric. Sometimes a student will ask why my correction is preferred to his sentence--what "rule" makes it sound better. And Cicero essentially says that rhythm is not primarily determined by reason but by the ear. How the ear determines such a thing, however, is somewhat of a mystery. We cannot find a "rule" that, when followed, will invariably produce an elegant sentence. But this does not negate the fact that there is such a thing as good rhythm. Under such circumstances, it seems that the only helpful way to teach rhythm is to provide many good examples for students to imitate and to correct bad examples, which is precisely what Cicero does.