Having worked on autos for years, and re-conditioning batteries, my advice is to properly clean your connections and then use the felt washers, These absorb and neutaralize the acid.
Either sandpaper, or steel wool works fine for cleaning, also you can buy a terminal cleaner which is handy if you maintain a lot of batteries, also nice to have in your maintenance kit is a battery filler which can fill to the proper level and always use
distilled water. Both can be purchased at about any auto parts store. Tap or well water contains minerals or chemicals that may shorten the life of your battery.
If you do wish to coat your terminals, do not use something that is non-conducting and doesn't dry. If you use something like silicone or grease, this can seep between the clamp and terminal causing no contact at that point raising connection resistance. I spray mine with any paint I have around.