Janelle, if you have some fabric scraps left over, stitch a few pieces together and then wash them to see if the color bleeds.
I agree that letting a wet quilt sit in the washer instead of drying it right away will surely increase the likelihood of bleed.
I generally toss the quilt into the dryer for a short pre-dry, so to speak, on a light setting. That seems to help prevent bleeding. Then I hang or lay it out flat to finish drying. My quilts are tough, though, and I don't mind drying machine-quilted Qs in the dryer on light settings.
The cloth dye-catchers seem to be helpful in my experience.
But I don't know the answer to the synthropol or retayne as I've never tried either product.