When I prewash -- which is seldom -- I use detergent and run it just like laundry. I always put similar colors together just as if I were washing clothes.
The first time I wash a quilt, I always use a color catcher even if I've prewashed the fabric.
I'm sure you will get tons of different opinions on this subject. It seems to be one we just can't all agree on. Listen to the advice and do what seems right for you.