Drip rail caulk?

i removed my seam sealer in the drip rails last year. My process was twisted wire (cable) brush on a grinder then lots of heat and a scraper to remove the bits that get stuck in the drip rail folds. you should get the seam sealer hot enough to smell it.

i then primered and used SEM high build self leveling seam sealer. it requires a special gun, and is expensive, but it is very easy to use and spreads to about the factory bumpy look. with a little smoothing it looks perfect.

http://www.semproducts.com/repair-seam-sealers/dual-mixtm-high-build-self-leveling-seam-sealer