I smother all my wiring connections in Vaseline. A bit messy when servicing but my connectors are still shiny after 10 years . Cheap, easy to use, self healing and if you want to get it well into a joint, use a hair dryer to melt it in. Then tape and cover as usual. I no longer use heat sealing connectors and proprietary connections as they all leak eventually and you can't see the damage until they fail. I prefer basic crimp connectors, loads of gloop and black tape. Rip the tape off, re-gloop and retape. Simple.
Incoming ......