Thanks for your informative comments. Two questions:
1. Did the two replacement boots solve your problems?
2. Can you suggest how to best apply the dielectric grease?
The replacement boots did solve my intermittent misfires and rough cold starts. As far as applying the dielectric grease, just put on some disposable rubber gloves and generously apply to the portion of the spark plug the boot will come in contact with. You can also apply some to the inside of the boot.