I tried the baseball bat thing and found that the bat simply sank into the tire, resulting in no change in the rear fender. What I ended up doing was making a simple tool, which is basically a piece of 3/8 inch by two inch steel about 8 inches long with a slot in it. Make the slot wide enough for the fender lip to slide into, then start at on end and slowly bend the fender lip up. You need to realize that you can't bend it all the way in one shot, so bend it a bit, then move down a couple inches and bend it again. The metal needs to be stretched to get it lay up against the fender, so you need to be patient and keep working at it, maybe even a coulple taps with a body hammer to get it right. But be careful not to whack it hard enough to make a reverse dent in the outer panel. Nothing looks worse than your quarter panel looking like a sack of walnuts...