I have a problem. I want to write in a certain kind of voice, which requires me to pay attention to prose numbers (or feet), but I cannot seem to phrase certain common terms and proper nouns so that it sounds the way I want without inflating the expression, making it violate principles of brevity. Does anyone know how I can accomplish my goal?
Poetic metre, clarity and brevity are the three corners of a triangle and everything which we write falls somewhere within its domain. Through careful word choice, we can minimize the distance between these three corners, but we can rarely achieve high marks in all three at once.
This is why poetry often needs to be studied and interpreted. It often abandons clarity and brevity in its dedication to metre. That is also why technical manuals are usually hard to read out loud. They sacrifice metre and sometimes brevity for the sake of clarity.
As an author, you need to choose your location within the domain of this triangle. Will your writing sometimes be lengthy but always flow easily off the reader's tongue? Will your pen speak brusquely, cutting directly to the points you wish to make, without consideration for word choice or flow?
From your question, you seem to prefer metre and brevity, which means that you must occasionally sacrifice clarity. To serve your two preferences, you will have to rely heavily on your reader's imagination, to bridge the gaps which you must leave open in service to word flow and word count. Feed their imaginations through careful choice of your characters, settings, and the subjects about which you write. Use preceding and following sentences to correct any clarity gaps in sentences where you have had to carefully choose your words. ...and when it really doesn't work, sleep on it. A better way to say the thing may occur to you tomorrow.
As for actually answering your question, I have two suggestions...
Buy a good thesaurus and use it. Choosing an obscure but appropriate word is a perfect example of sacrificing clarity for metre and brevity. Challenge your readers to expand their vocabularies.
Read authors who share your love of metre and brevity. Consider listening to your favorite authors in audiobook form, as that medium really amplifies metre issues. When you find an author whose audiobooks sound like they were written to be spoken out loud, that is the author you are looking for. Study everything they have written.