I’d recommend blunting the nails first. I’ve not used this methods for turnings, but I used to for flatwork. That said, the nails almost always left a mark albeit minute.I just use small scraps of plywood with a finish nail driven through them. 3 pieces gives you a 3-point stance so as to not have much in the way of wobble, they are easy and quick (and very cheap) to make as many as you like..... for smaller bowls, a larger scrap with 3 nails driven through it would serve the purpose nicely, I imagine.