Removal of the cardboard pier footing forms in the crawlspace – how to do it

For that size hole, I'd probably go with a Post Hole Digger. If it's sharp and there aren't too many rocks or roots, you just shove it into the ground, pull the handles apart, and lift.

However, for the number you're going to be digging, it might be better to visit your local tool rental shop, and rent a gas powered auger. If you can get a second person, the two person models are a lot easier to control ... you can then square it off with a shovel, and either get the last bit out by hand, or with a post hole digger.

You need to place the footings deeper than the frost line. Some research says the frost line in CT is around 42" so you'd do well to put the posts down 48".

The city will be able to verify this when you get your permit approved.

Count yourself lucky... In Ottawa, Ontario I had to put them down 60"... and they still heaved one year.