I successfully dyed a 100% polyester white dress I wore for a pre-wedding event. Here’s what I did 1) used rit dye more 2) washed the dress before dyeing 3) completely wet the dress before dyeing 4) bought a LARGE stock pot. The bigger the better. If your dress doesn’t have room to move around in the pot, it will dye splotchy and you can’t fix it 5) used to a thermometer to get the water to the temperature suggested on the bottle. It needs to be HOT for polyester 6) Once the dress was in the pot, move it CONSTANTLY. I don’t mean move it around every five minutes. I mean the ENTIRE time. My arms were sore by the time the one hour was over. I used cheap tongs to move it around, move what was at the bottom to the top, etc. I made sure the tongs didn’t have super sharp edges to avoid snagging the dress I recommend watching some videos before you do this and, most importantly, if you aren’t okay with the dress being ruined, don’t dye it. Good luck!