I've had much better luck with a little Dawn dish soap, a LOT of very hot water, and time.
For what it's worth, this quilter and hand-dyer tested a bunch of different products and found that this combo (Dawn, hot water, time) worked better than Retayne, Synthrapol, and Rit dye fix.
https://www.colorwaysbyvicki.com/sav...ing-quilt.html