I want to be sure I cover all gray hair. What should I do?

For the deepest, richest color choose an AGEbeautiful shade in the same level as the brand your client typically uses. So, if the client typically uses 6N, select 6N in AGEbeautiful. Increase your processing time and use a 20-volume developer. Apply in thin, fine, 1/8”partings so hair is thoroughly saturated.