Cutting the first few sheets of paper by hand to make confetti will go well until you get into cutting up the thin strips which do not want to cooperate. You will slow down to a crawl.
You must automate this process.
To produce the confetti yourself, use a cross-cut paper shredder which produces chips/chads instead of strips of paper produced by most others.
Place the shredder over a large waste paper basket lined with a garbage bag so that you won't have to empty it often.
You can borrow, or rent a shredder if you look around and try the various flea markets and used equipment online listings. Advertise in the listings to make a contact to get the job done.
If you can get your paper supplied in rolls, you can feed several ends into the mouth of the shredder at one time and it will be self-feeding. You can use up to 6 rolls of 20 lb/85 gsm paper stock.
Paper when "fluffed up" this way will produce up to 50 times the original volume so have plenty of bags handy for the amount you will produce.
You can visit a paper shredder company such as Shred-it to generate massive amounts of your supplied paper as well as a do-it-yourself. Bring your own paper as they treat all materials as confidential and cannot supply their customer's waste for you.