This was the most difficult part of re-assembling my car when I restored it. I don't think there is any good way outside of a lot of patience. I found starting from the top and working it down (to RagTop's point) worked the best. I also used a little dry soap (rubbed along the bottom edge) to help keep from scratching the paint and lubricate it a bit. Work from the caps to the ends like RagTop suggests. After I got the molding back on (it was still a little loose), I used a 1/4 x 3" piece of soft pine and tapped the bottom lip to secure it along the entire length.