I use silicone grease like dielectric grease, (not silicone rtv sealant). Just coat the rubber gaskets, o-rings or whatever gasket you have and a little on the metal surfaces and it'll waterproof it really nice. That's what I've used for years in car accessory wiring that go through firewalls roofs etc. Never had a leaker yetdo i have to use some silicon under and above the gasket. seller said no but figured id ask. im thinking good insurance. silicone grease or rtv?