Ron Burgundy wrote:..but, I read everything you cited, and anti-seize is still the way to go for salt water use, which is where I boat.
From everything I have read it clearly states that
NEW plugs come with a anti-seize metal coating so it isn't necessary to apply anti-seize on the
INITIAL installation. However, once they are removed the factory applied anti-seize metal coating is no longer active.
...so if you take out your plugs to inspect them,
AND you use your boat in SALT water it is only logical to apply a thin coat of anti-seize to the threads
and be sure to not over tighten.
...Am I missing anything??
...besides my sawback

1. You've already covered the important difference between high temp nickle and copper based anti-seize. Any brand will be fine, and you can buy a lifetime supply at your local hardware store for the same price you would pay for tiny "branded" tube. While you're there buy an "acid" brush to apply it. It has short, rather stout bristles and is dirt cheap.
2. Cleaning the female hole threads with a cylindrical
stainless steel wire brush - the kind used to prep the interior of copper tubing before soldering - would be an excellent idea as well. Just be careful not to push any debris INTO the head. I like to screw it in part way into the hole, then directly pull it out and clean it - then repeat several times going a little deeper each time, until you have reached the ends of the threads. A final cleaning with a used toothbrush - drawing it outward - should leave the threads in pristine condition.
3. I also like to smear a VERY thin coating of dielectric grease on the top of the plug to inhibit corrosion. It also helps to ensure a good electrical contact and will often allow the rubber boot to simply pop off next time - instead of having to forcefully tug on it. I've caused myself a lot of grief in the past by having to pull so hard I trashed either the boot or pulled the lead completely out of it - even after having used a boot puller tool on it.
...and then, as professor Henry Higgins said:
"By Jove, I think (he's) got it!"