I think you should high light the whole works, it will help it to blend, and make you look younger, too. Why do you want natural color salt and pepper hair, anyway? 20 years, added on, I'm telling you.
How Can I Remove Hair Color Light Brown Dye And Go To Natural Color - Salt And Pepper?
What I did when I decided that my hair looked better without dying it was to have my hair highlighted with blond highlights. It made the change more gradual and I could tell when it was all grown out.