I prefer SEM #39777 -High Build Self Leveling Seam Sealer- but it does require the double barrel gun which is kinda pricey. The seam sealer itself is not cheap either- about $40 out the door here.
Do as Coronet and chevy_power say and also dam up the ends of the drip rails with tape to keep the sealer from running out. Also the SEM sealer is sandable so you can smooth it out if you need to.
Wow, I have never had any problems like that. I'll give the SEM a try next time based on your recommendation.I use SEM seam sealer as well, I prefer it over any other seam sealers I have used, I have had some major issues with the Fusor 1 part seam sealers, we applied it to a whole car and after a week you could rub it right off with your fingers, I also find that the SEM 2-part goes a LOT farther for some reason.