Hello. I am 41 years old and am finding more and more gray hair all the time. This hair is coarser than my other hair and it is also much (!) more difficult to color. In fact, the last time I colored my hair, a friend remarked that I looked like I had strands of tensil laced through my hair because there was still so much silver. May I ask, please, how well does your product cover this type of coarse gray hair? Thank you for your time...