Writing, speaking, and reading are inseparably connected. If we want to be good speakers, we should also try to imitate, listening to and reading the best authors. No one author is perfect, so we should read a variety of the best. We should also read poetry, imitating what is good. Then, we should seek to excel and be even better than those we are reading. Those expert writers were different in their day than we are in ours, of course, so we shouldn't try to imitate them perfectly.
The pen is the best teacher of eloquence. Great difficulty precedes true excellence, but we shouldn’t try to perfect every tiny little thing in every sentence—meaning we can’t be perfectionists. Quintilian says he doesn’t know who’s worse: those who are pleased by everything they write, or those who are pleased by nothing they write. How can we perform our duty to the public if we’re always trying to perfect everything and revise what we’re writing instead of doing our best in the time allotted and then publishing it? We can only write and speak according to our ability, so we shouldn’t become annoyed with ourselves. We must not be idle; nor must we make excuses to not study until our minds are fresh or we are “feeling like it.”
In short, there’s no value in an orator who takes too long to produce something.
Translating is also useful. So is meditation. And memory.