I am making a couple of bookcases for a friend. The cases are made of 3/4 cabinet grade plywood. I have cut some poplar for the face framing to cover the edges of the plywood. I have some saw marks on some of the poplar facing. What I want to know is how much sanding should I attempt to do? I'm tempted to sand them all off, some are pretty bad. They plan on painting the whole thing white. They plan on 2 coats of primer, followed by the color of their choice. Would I be wasting my time to sand those marks off? I just don't want those burn marks to "show" through the paint. Any words of wisdom here? Please..