You will be able to see clearly, where the shaved hair is re-growing in comparison to the hair you want to keep ....... I did mine yesterday standing in front of bathroom mirror hanging on the wall and just used a medium sized hand-held mirror to see around the back area --- you will have no bother/worries once it`s been done by your professional, you will see the difference . The re -growing hair is stubbly/ much shorter than the un-cut hair. It shouldn`t be an issue for you whatsoever. Best wishes, Paul.