Female molds do not depend on sanding the tool surface to completely vent. You must properly port the tool to make that happen. Surface sanding is used only in cases where local areas of a tool surface cant vent to the facet edge. This is different from porting. It is possible to get the tool too smooth and sanding will help that, but there is no RULE about it. It's an on demand cure for a specific issue. Finish the tool, pull a part or 2, look at what issues you need to cure. If you can't tune it, come back with specific questions/photos and we'll get them up.