Good post Sabotloader. I also like a tight fitting no.11 cap to help make rain/water proof. I like to slip a cap protector over top to help seal the seam between the cap and plug when hunting in wet weather.
This has never really been a concern for me but I remember one wet hunt where we had nailpolish painted on the cap that seemed to keep things dry... just not a good idea to store the gun with a cap on it... so what do you do at the end of the day... if like me... "kaboom"... but nipple protectors, clear plastic airhose with a piece of paper or hot glue (or both) work swimmingly for that... and almost free...