what to use to seal inside of doors behind door panel?
My wife works for a company that makes the plastic sheeting used to cover bundles of lumber seen shiping on trains. Fiber reinforced plastic sheeting always on hand here. LOL Your local lumber yard may give some to you.
The imports like Honda use an adhesive that is somewhat like white lithium grease. They use the same stuff on bulbs in the light fixtures. It allows removal and reattaching the plastic sheeting where service is required.