I don't prewash fabric, so I am particularly careful with the first washing of a quilt. If there are bleeds, I do not want them to discolor neighboring fabrics. What I do is take the quilt to our local laundromat and wash it in their largest front-loading machine. This ensures that there will be enough water to dilute bleeds. I also use Synthrapol and wash in hot water (Synthrapol requires hot water to work).
It's important to use enough water to dilute any bleeds. In my opinion, Shout color catchers are not enough if you are not using lots of water and/or if there is a major bleed.
If you have some of the black fabric left, you can test it to see if it is going to bleed a lot. Drop a square in a clear glass of water and let it sit for a day. If you see wisps of dye color in the water, it is going to bleed. If you can't see any dye, rub the dampened fabric against other fabrics in your quilt to see if any dye transfers ("crocking"). If it passes both these tests, you are safe against a major bleeding problem.