We know you love mixing up fun, vibrant color formulas for your most adventurous clients, but don’t forget about the service that brings in the big bucks—gray coverage. Although it’s not the most glamorous job, it’s one of the most important, so you have to know how to do it, and do it right! To keep your skills in check, Terri Adams, TIGI® Senior Director of Hair Colour Education and Business Development for the Americas and coverage master, lets us in on all her secrets, so you can help your clients age subtly and keep the gray away,…