If you want to get the best flavor, I highly recommend grinding your beans fresh rather than using preground coffee.
For this much coffee, I definitely recommend using an Electric Coffee Grinder. I use this one myself and it works great.
For the most consistent grind, the best hand grinder is definitely the Hario Ceramic Coffee Mill
If you want a cheaper, better looking grinder, I use this Stainless Steel Coffee Grinder
If you have any questions about the coldbrew making process, please comment below! And share with your summer-lovin, coffee-drinking friends!