The classic for blood bait is chicken blood that's been poured to about 1/4" thick in a baking sheet, then allowed to coagulate in the refrigerator. You then cut the coagulated blood into strips about one inch wide and 4 inches long. A good way to fish it is by leaving a tag line of dacron on your treble hook, then wrapping the blood carefully on the treble and looping the dacron over the blood to secure it to the hook. You can freeze the strips and they'll keep for a long time.
It works, but it doesn't last long: 15 minutes max. It works best when you're fishing for eating sized channel cats in a hole with snags in it. Pour a pint of fresh blood at a time upstream of the snags to activate the cats, then fish your blood bait. Another problem with blood baits is that it can be an ungodly mess. It's hard not to get it on your clothes and under your fingernails. It's hard to wash off of things, especially plastic coolers and such.
All this said, I still prefer cut bait or night crawlers for channel cats. They're easier to work with and they are at least as effective as anything else. Call me a catfishing iconoclast, but I don't go for the messy stinky baits. Fact is, channel cats are most likely to eat things they're familiar with, so I stick with the familiar and it works for me. It also gives me a better shot at catching some other species in the river.