Re: A few important questions.
There is no blood in meat. There is a little serum, but that's it. I'm vegan, so trust me -- I was WAY more grossed out about the whole thing at first than 99% of folks, LOL. And I can do it.
Chicken hearts are nice if you're grossed out b/c you don't have to cut them. Just toss a few in a bowl and that's that. Beef/pork hearts must be cut up for cats.
One way to reduce the gross factor w/ this stuff (and make it easier to cut up) is to freeze it and then PARTIALLY thaw it. This makes it firm and easier to cut (plus less serum-y). This is esp. helpful w/ liver and kidney, which are a total PITA (and gross!) to cut up. When I get liver, I freeze it, partially thaw it, then cut up half of it into cat pieces and half of it into dog pieces. Goes into baggies marked --L-D or L-C. Then I re-freeze and thaw when I need them to feed.