Not at the Fortress, but I had a newer domme at a house location I sessioned with who did whipping. I had never done this activity before, but she suggested it and even used saran wrap to maybe help on the skin, but it didn't. I disliked it on my back and I had marks for weeks. She also was using one of those rolling wheel spike devices that you run on the skin, but for some reason decided to lift it and hit a few times around the head of my dick, thus producing some blood.
It helped that she was young and hot, but I make sure now to request nothing on my back before every session. I actually sessioned with her again 6 months later and it was great, she learned alot more since first starting out and seems to have really grown since then.