What grease (or similar) in license plate holes?

I have just spent quite a few hours playing around with POR-15 on my other car (not a Prius) and also drilling out a rusted bolt when I had to change the plate (thing was totally rusted in and I even took the impact screwdriver to it!).

On that vehicle, and others I see on the road, there is often rust on the back around the license plate area. I believe that the license plate's metal resting up against the paint is awful on paint, so I've put a few daps of silicone on the back of my plate before putting it back onto the car (yes, I let that silicone dry!). But also I want to lube up the holes where the screws go in. I'm less concerned with them locking into the threads (anti-seize would solve that) than I am moisture just "hanging around" that area and rusting out where the screw goes.

Any ideas on good greases? I cannot find for example if lithium brake grease is safe on paint. I know car wax is obviously but it has a limited lifespan.

I'm pretty sure most people just apply their plates straight into the car and I am pretty sure it's a bad thing to do as years down the line it can cause issues.

 

Tape coudl work but would only seal the threads. I was in lowes and the silicone lube spray says specifically safe for paint but I am not sure whether the silicone brake grease would be also safe (I said lithium in first post, meant silicone).

 

On the Prius they may. It does appear that the dealer used plastic screws in this case so I'm good to go. I'm surprised not everyone has been using plastic for years, it just makes so much sense in this case.