Thanks for the quick reply. Where exactly did you apply the grease? The heat shrink probably around the cable connections? If you happen to have a picture, I'd appreciate it!
The dielectric grease goes directly on the contacts and pins inside the plug.
I have an eGR and I elected not to use the rubber cement or any other glues or sealants. I just used dielectric grease on the ports.
But... eGR hasn't had water ingress issues that I'm aware of. Really, all the grease is doing, I think, is helping waterproof the electrical connections, not prevent water from getting INSIDE of the derailleur. The other methods are, I think, ways to try to keep water from getting inside of the derailleur. If it functions correctly, that should never be an issue.