You're right.. The bore of a brass jet is easily damaged and just a scratch might change it's flow rate. Don't use hard wire or any hard tool near a jet unless you are extremely careful. I prefer a single strand of soft copper wire from a small wire cable if i'm forced to poke something out of a jet's hole.
An idle jet's hole might be so tiny that you won't find anything that fits in it. A good soaking in solvent followed by compressed air blast should do it. First make sure it's actually clogged before moving on to any sort of mechanical cleaning.
I sometimes use kerosene in an ultrasonic jewelry cleaner but thats another story for another day. Liquids in ultrasonic cleaners get hot and kerosene is flamable.. caution!