I brush oil on the skins before we sauce. Like Dave said, the high-moisture pizzas seem to have more of a problem. For our vegetarian pizza, we started sprinkling Japanese bread crumbs (Panko) on top of the cheese before the toppings. It really helps to soak in the extra moisture. After it’s baked, you’d never know the bread crumbs were there. There is a commercial product that does the same thing, but Panko is about 20% the cost.