I used it with my previous piece that was less gray... so I have not had to do it again since the new one came out more gray (although they were ordered the same). With the old one I did it two different times about 4 weeks apart. How often really depends on how long your side hair is.... the roots are not as critical here since you really can't see them except for the temple which I applied a lot less coloring to anyways since it's normal for temples to be more gray.

I applied it with my hair off... it would be too difficult to do it with it on.

NCC