I don't think he was suggesting you use peanut butter, he was suggesting using a mix of baking soda the consistency of peanut butter...
I've never had an issue with the sprays, just a light coating prevents fouling for 4-5 years. You don't need to go bonkers with it. You do need to use both sprays though, just the protectant only lasts about 1-2 years. Clean then protect.
You can use dielectric grease, just in moderation. If you use too much, you get the problem Stubbyie is talking about, eventual degradation of the current flow capability of the connection. I use it all the time on spark plugs, it's the only way I can get the wires to release from the plug caps! But it's a light coating. As long as whatever metal makes contact 'bites' through to the opposite metal, you are fine. If it's just a surface to surface mating, it can cause current flow issues.
There are conductive greases out there but they can have their own issues, if you get the spread too far out from the contacts, they will conduct along surfaces that are supposed to prevent it and you end up with power going where it is not supposed to.
FYI, you can use a clear laquer, shellac or enamel AFTER you have all the connections in and tight. This will prevent the battery gases from forming the corrosive oxidization on the terminals as well, but you need to clean it off if you take apart the connections and intend to reconnect them.