I went from Natural virgin hair to texlaxed about a month ago and things have been going pretty well.
My natural hair was 3c/4a/4b and I had it pressed and trimmed about 6 days before the relaxer process. I would do it differently if I had the chance because after 6 days my scalp was itching like crazy (it's use to shampoo every 3-4 days) but I couldn't scratch for fear of irritating my scalp before the relaxer). I'd probably shampoo 3-4 beforehand, not 6.
As for the protein ahead of time, I did a treatment that same day I shampooed so 6 days ahead. Also, the reconstructor/protein treatment I used after
was very helpful. The phyto comes with this "Milky restructurer" that was good with stopping any breakage from occuring after relaxing. I actually used that about 3 times during the week following the process.
HTH a lil bit. Good luck! I'm sure you'll love it