clay itsnt water (liquid proof) but small screw threds can be hard to tape off. I would just park the whole screw and chase threads with a die later if you have difficulty installing the screw. If you have access to Parkerizing equipment you probably have access to Dies of the appropriate size. You know what they say about assumptions though...
To sum it up: Somewhere there is a TRUE BELIEVER training, he will not stop in his mission, he knows only the cause. What have you done today? For your brothers at arms, friends, family, your country, yourself?