So I originally purchased this for my son. So I tried it, and I was very surprised of how well it worked. I will say it works best on the line work, shading it will definitely wear off fast. I guess you could always stop and reapply. My 17 year old did use it on his ribs, and didn’t feel anything until the shading. I asked him a few times if he wanted to reapply, he didn’t want too. But yes it does work.