Highlighting back of your head?

Good question. I was faced with this problem last night. I wanted to add more highlights to the back of my hair (because I missed a few areas the first time). I ended up propping up two mirrors facing each other so I could see the back and front simultaneously.

I don't know anything about the cap. Sorry. My hair's too long for it. I used a mascara wand to do my highlights last night. I've also used a denture brush, a toothbrush and my fingers.

P.S. Do you have a friend you would trust your hair to? That's the easiest way to highlight the back of your hair. I've gotten my sister to do foils for me before. I never could have done it myself.