Hi Jim,
Took me a while to get back to you. Practice is always good and the durablocks are great. I used a combination of those and the 27" AFS (adjustable flexibility sander). I don't know how far you have gotten with the quarter panel but use of a good 4 foot level would be a great place to start just to see how bad the previous damage really is and to consistently check you progress for accuracy against the other side. Hopefully it wasn't bad enough to compress the inner wheel housing! If so, that adds a bit of time and fabrication skills into the fray. Sounds like someone sideswiped the PO or he got into a pole. Good call on that one :-). Keep in touch. I would love to see some pictures of your current progress and maybe one with a flat edge against your damaged panel stripped to bare metal. There is a chance you may be able to salvage the quarter with some righteous metal work :-).
Chris