Trimming Beaks

So I was wondering how you go about trimming a beak that has already been overgrown. I don't know of any vets that will do it, and was wondering if anyone had any snazzy tricks that they've found or any simple procedure that could be self done.
And a follow down question is how do you keep a beak from getting overgrown. I've heard about putting cuttlefish bone in their enclosure and that does not seem to work, and hard foods like melon rinds, also doesn't work as it doesn't really seem to cause enough frictional abrasion on the beaks to keep them in check. Thank you Fauna community.