I would use any method that calls to you… You can stand up and declare it, you can use white light or sage the same way you’d banish a room but imbue the energy intentionally that you are naming this knife, you can enchant it, which is similar to conversating it, you can have a little dedication ceremony.
We have a collection of tutorials for enchanting things. Unofficial Tutorials: Talismans, Amulets, Rings and Enchanted Things Collection
And if you are short of time, simply ground yourself, point at the thing and say with intention “I name you X” and so it is.