Hey Josh,
I use to use 2 liter pop bottles filled with the expandable spray foam insulation. Now I use foam noodles that you can find at Wal-Mart or Bass Pro (like these). I'm not sure how big of catfish they'll hold, but I know a 23lb Flathead can't keep 'em under.
I rig my jugs with lines varying from about 8 to 20 feet. I use a large barrel swivel at the jug and a snap swivel at the hooks. Cats, especially Blues and Channels, love to twist, so you need swivels. Also, you may catch Channels and Flatheads near the bottom, but there is no telling where you'll catch the Blues. I've caught many of them at 3 feet deep over 25 fow. That's why I use varying line lengths.
I use 2 to 8 oz weights, depending on how much wind or current there is. I tie the weight at the end and then I make two droppers about 3 to 5 feet apart. I put snap swivels on these loops so I can quickly change out dull hooks. I use 5/0 to 8/0 Circle Hooks.
I like my jugs to move along with the wind or current. You'll cover more ground this way and find the active fish. I don't anchor my jugs out. I prefer to float along and watch 'em disappear. These catfish here came from my jugs. I use 10 and keep them in a 5 gallon bucket. It's a tight fit, but it keeps them somewhat organized!