Homemade Primers - Dedimple and Resize
If you have access to machining/tooling - this method is awesome. It will press out the dimple from the cup (de-dimple). It is relatively fast and doesn't damage the cup (like my earlier method). In fact, this repairs the cup because it resizes the cup in the same operation. Resizing the cup resembles resizing your brass - gets the material back to round.