Dyeing 100% Polyester Chiffon Bridesmaid Dress

One of my most recent projects has been learning to dye polyester fabric. "Dye" is probably the wrong word - it's more of a stain, since it's basically soft, woven plastic. 

It all started when I realized after some Google image browsing that the lovely bridesmaid dress I'd ordered for my friend wedding was probably not coming in the burgundy shade I had set out to find. The tiny fabric swatch and color block suggested a dark wine, but I was finding customer reviews with phrases like "oh and by the way, it's more of a true red than a maroon." Not encouraging.  Of course there are no returns on things like this, and while Jenny is ridiculously accommodating, not demanding, and probably the anti-bridezilla, I didn't want to wreck the lovely color scheme with my fire engine red dress. My options, it seemed, were to either buy a new dress ($$$, and probably too late anyway) or to try my hand at dyeing.
You can imagine my chagrin when my initial research turned up the fact that it's almost impossible to achieve a strong dye set on polyester fabric, even with harsh, toxic chemicals and very high heat. Both options would likely to destroy my delicate garment with the bossy Dry Clean Only on the label, but further digging revealed that a tint was possible. This tutorial from College Fashion for using Rit Dye showed that while a vibrant color was out of the question, I might be able to add enough of a tint to change the bright red to something darker.
Eventually, with encouragement from various tutorials, I bought two bottles of black Rit Dye (around $4/bottle, or $2.50 for the smaller boxes of powder) at the grocery store and a yard of similar fabric from Joann's and set to testing. The results were good, if not mind-blowing, so I nervously cut the tags off, grabbed Joel to take some pictures, and got to work.