I found a set of type 8 mirrors for my truck at a salvage yard. In order to install them, I have to drill 5 holes in each door. Most of the mirrors that are attached to doors like this have "rust drip" where you can see a rust stain from the hole. Some are just plain rusted completely out. The bolts are stainless torx screws, and there is some type of washer/gasket for each hole. They are not rubber, but teflon or hard plastic of some sort. So, is there any kind of rust preventer I could apply, or would rubber grommets work best, or maybe even silicone caulk applied at time of installation. What do you think?

 

Silicone will only make it rust quicker. I would just buy a touch up paint brush bottle from parts store and paint that and wait for it to dry. Doesn't even have to match just get close but if you can get it to match then you can use it on nicks etc.