The birds that can be processed at 8 weeks are those special hybrid Cornish Xs, and maybe some of those free-range broilers. I don't do my standards or mixed-breeds until 18-20 weeks, they're just too skinny before that. I haven't yet had one that was tough or bad tasting at that age.
I processed 5 birds today using the technique shown on the YouTube video titled "Chicken Processing on Custer Family Farm". They show an easy way to skin the birds and also an easy way to gut them. Even if you decide to pluck your birds you can still use their technique for cleaning out the carcasses. There really isn't any blood to deal with except what comes out when you slice their throats or chop off their heads. When you cut into the body cavity there is no blood to deal with.
If you put the birds in a cage with only water to drink, no food to eat & not even any grass to grab, there should be little to no contents in their crops or intestines.
