This stuff has prevented corrosion on numerous batteries I've installed, just paint both the post clamp and the post with it (after cleaning them with a wire brush first) and hook them up. Wipe off any excess, don't cake it on.
I also use it to keep wheels from sticking to the hub-centric cone on an axle from corrosion (I've found forged aluminum wheels to be horrible for this)
https://www.calfast.com/12245-JEL102...iABEgJ9oPD_BwE
Jet Lube's SS-30 is also good for the same purpose and even notes the battery post use on its packaging. Its a bit thicker than the Kopr-Kote
https://www.jetlube.com/pages/SS30.html