Ice dye project

OK... I've ice-dyed once before in a workshop so I didn't really know the behind the scenes stuff that was going on...
I want to do a base dye and then over it with ice dye. I am using silk chiffon (I don't want any white to show when I'm done) I have the following goodies from Dharma: Dyer's detergent, Soda Ash & Procion dyes.

General Question: Do I need to "scour" the fabric first?

For the base dye:

- do I need to soak in soda ash? for how long? I've seen conflicting info on the internet - some say 15 min, some say 6hrs.

- do I need to dye immediately after the soda ash soak? Or can I soak one day, then rewet and dye the next?

- If I'm going to ice dye over it, do I need to wash with dyers detergent first?

For the ice dying

- do I need to re-soak in soda ash? I'm guessing it depends if I washed it or not??

- and again, do I need to dye immediately after the soda ash soak? Or can I soak one day, then rewet and dye the next?

(I also have cotton and silk that I'm testing as a lining, but I'm really not as concerned with that since it's just going to be a solid color

THANK YOU THANK YOU THANK YOU!!!