Use your mixer! I use my kitchenaid mixer but a hand mixer will also work. I can throw the hot cooked chicken breasts right in and the mixer shreds them up easily. The key is to do quick bursts of the mixer, don't just turn it on full blast or it'll throw the chicken right out of the bowl. If you're doing a large batch, put just a few breasts in at once, pulse it until you like the level of shredding, then dump it into a large bowl to the side and do the next few breasts. Repeat until it's all shredded.
You can cook large batches of chicken in a crock pot, but it takes hours to cook them. Still better than boiling, but not super fast.
THEN I got my Instant Pot. Hello! Now I don't even have to deal with boiling chicken anymore OR waiting on the crock pot! I can cook 5 lbs of chicken at once - I just throw it in the instant pot with some water, set it to pressure cook for 15 minutes, and walk away.
I actually keep cooked, shredded chicken in my freezer now so I can use it in recipes as needed. I even keep some seasoned with taco seasoning to use on a taco salad or in a lettuce wrap. So convenient!
Some recipes from this blog that you can make with precooked shredded chicken:
Chicken Fajita (P3)
Chicken Apple Slaw (P2)
Chicken Spinach Tomato Soup (P2)
Enchilada (just sub chicken for beef) (P2)
Chicken Soup (P2)
Chicken Chili (P2)
Chicken Salad (P3)