i'v never used anything but a mix of different liquid dyes for blends like this.. but need a powder for a ice dye. thanks for the help !! 
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Jacquardmod Jacquardmod
The problem is that polyester absolutely has to be heated for it to work.  You cannot ice dye it under any circumstances I can think of in that way, unless you let the Idye poly get on the clothing through the melted ice and then go back with a heat press to fix the dye where it falls.  I don't think an iron will do it, but it might be possible.   

For the rayon you should be using a procion mx dye.  You have to pretreat with soda ash.  Procion is the best for ice dyeing because it does not require heat to achieve intense colors unlike other dyes.  
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