vinegar only works to set acid dyes...if it is not an acid dye you are only wasting vinegar.
i would experiment with the scrap you have to find an answer putting synthropol in the water (bought in quilt shops and other textile type craft/hobbie shops) it will keep the dye from getting on the other fabrics as you wash it away. the color catchers help too- but i would use the synthropol in the water (it is a detergent)
color catchers are in the laundry isle of the grocery store- come in a box that looks like bounce sheets...is usually near the shout- spot cleaners/stain removers.