Can I use other brands products with keratin hair products to get smooth hair?

I know that I can use keratin’s shampoo and conditioner to get smooth hair. But my friend suggested me to use sulfate free conditioner with keratin’s shampoo. She says these sulfate free products will make my hair silky and shiny and has a protestant for when I straighten. So if I am using keratin hair shampoo then which sulfates free conditioner I can use with this shampoo to get smooth hair?