Hmmm...I think it would be better to put either straight silk protein or whatever product you have containing the silk protein on the hair first (if it's a conditioner, let it dry first) and then apply the relaxer because if you mix it in together, the silk and the ingredients in the relaxer are going to blend together and hit the hair at the same time, which would kinda defeat the purpose. You want the silk protein to provide a protective barrier so when the relaxer hits, it encounters a "damage roadblock" with the silk.
As for conditioners/products I know that have silk protein:
1. CHI Silk Infusion
2. Motions Silk Protein Conditioner
3.
http://www.lotioncrafter.com/store/Silk-Amino-Acids-pr-16295.html (Straight silk amino acids, which I will soon be purchasing)
4.
http://www.healthyhairplus.com/HairProducts/silkprotein.htm (another silk protein conditioner)
5.
J. F. Lazartigue Silk Protein Spray
6. CHI Infra Thermal Protective Treatment
7. CHI Shine Infusion Thermal Polishing Spray (just looked on the back and saw that it contains hydrolyzed silk, but it's like the second to last ingredient right before butane)
I'm interested in seeing what other products or conditioners contain silk that I do not have or haven't just looked up haha.