I did some rust dyeing and made one oops that you can learn from. I got some yummy fabrics. Even some of the synthetics too color.
My process?
Soak fabric in vinegar water for about an hour.
Wrap various metal pieces in fabric.
Keep moist with more vinegar until color makes you happy.
Rinse in a salt water bath then in clean water until it rinses clear.
***ALWAYS wear gloves
*** DO NOT put items in an aluminum pan
Etsy: https://www.etsy.com/shop/SusanTaylorBrown