There are two kinds of quilters. Those who wash everything, and those who wash very little. I don't wash the fabrics I buy, unless it is going to be a quilt that gets washed. Most of what I make is for competion, and will just hang on a wall. But, for my Hoffman Challenge, I washed everything. It will be traveling for over a year, and who knows what it will look like (or what will happen to it along the way) when I get it back.
That being said, I almost always wash reds. Too dangerous not to. But, you are right in not washing your precuts. All you need to do is wash the finished project in sythropol, following the directions on the bottle. As I understand it, the sythropol will keep the left over dyes from reattaching in other areas. And, there are washing aids that will also set the dyes. Having never done this, I am not familiar with them, so will not expound on that.
Also, I always take a small amount of each of the fabrics that I am going to use, and soak them in hot water. If it bleeds, I rinse it and soak it again. If it continues to bleed after 3 or 4 soaks, I do not use it! It's just safer for me not to.
Dawn