I would use the Retayne first before construction, but just to be sure ... when washed use Synthropol. Better safe ... than...

When I dye fabric, I use an old salad spinner to get the excess colored water out, in between rinses. It speeds the process, but I'd still use the Retayne. It only takes a teaspoon to treat a yard of fabric, so you can buy the small size.

That is great to know. I am going to pick up Retayne and just keep it in the house.
Thank you all.