Have you cranked up the vacuum cleaner near him yet? That usually sets my flock off.
Or brought him in the shower? Kiwi doesn't have a large vocabulary or range of noises, but the vacuum and shower seem to be the 2 things that encourage him to make every sound/word he knows! But not every bird is a talker or even a squawker.
My amazon is only 16, and we adopted him when he was 10. He has not picked up ANY new words or noises since we got him. We don't encourage speech, if he wants to talk, he will, if not, that's ok too. He mainly makes a goose honk, high pitched "weeeet" noise and owl hoot along with the standard amazon screech and alarm call. He will say "hello" in a deep mans voice (usually when he wants something), "hi" in a little girls voice and the first half of the wolf whistle (and he expects you to make the second half back to him:54

. He thankfully, seems to have 'forgotten' the curse word he knew how to say (in context) and now makes a garbled parrot noise instead (though he still makes that noise "in context" :31

. He was clearly told that more than a few times by someone! My mom has a 43 y/o green cheek amazon who screeches when you mention a favored food, squeals like a pig when you bother him and occasionally flock calls his mate, but is otherwise totally silent. The 45+ y/o DYH makes a full range of countless (beautiful and pleasant) 'wild' parrot noises, but has never spoken human words.
Just an opinion, but I would go with the flow on the talking. If Charlie is a talker, he will naturally pick things up. If he isn't and you sit there and repeat a word or noise a thousand times until he does pick it up, well, he's going to repeat that same thing right on back to you until it drives you up the wall (I know people with a bird who says the same thing over and over and over and it just drives you crazy after a while). The natural talkers I hear don't just repeat like ones who have been "taught". They interject words (often in context) into their normal vocalization patterns, which is adorable and not annoying.