I never prewash. I only wash after I am finished if I know it's going to be a use quilt. However, whether prewashing or not, I would recommend using Color Catchers or that other color wash. Retayne would be good as well.
I just washed a quilt I gave my son that has red in it and had run (he didn't wash it properly). I used a bleach alternative, several Color Catchers, and cold water wash. The quilt now looks whiter and the Color Catchers were very red.