What is the correct way to lubricate the connector?

Lubrication is an art.

• The Goal: The grease is there to reduce friction and allow the rubber to slide, not to act as a sealant itself.
• Application: Put a small amount on your finger (using a nitrile glove) or a swab. Lightly coat the circumference of the male pins and the inner rim of the female socket.
• Warning: Do not fill the socket holes with grease paste! This will prevent electrical contact and can cause the connector to pop back open due to trapped pressure.