This is how I climb grattons on a slab. It turns them into jug ladders and it uses up zero skin.I've seen fingernails being used on grattons where the nails are wedged into the little gap at the back of a gratton. The distal bone is pointing down. I went to find some slopers.
It's no use when they get steeper and you have to pull harder. At that point, I go and find something more pleasant to use my finite skin supply on.