This article is from the Chrysler-Plymouth-Dodge FAQ, by Dr. David Zatz with numerous contributions by others.
Marvin Stockman <(e-mail address removed).navy.mil> reports: I usually
purchase a caulking gun sized tube of black GE Silicon II sealant. Clean
off the damaged weatherstripping with alcohol or other suitable cleaner.
Apply an appropriate amount of sealer to damaged area. Cover area with
plastic kitchen wrap and with sealer covered form to an appropriate shape.
Close door. Car can be used and door can be opened and closed, but don't
remove plastic for 3 or 4 days. Don't use Saran wrap as most silicone
sealers need moisture to set and Saran is too good a vapor barrior. I
have done this for many years on many cars.