how to fix up bulkhead connector?

Del, et al: I'm getting a bunch of voltage drop anomalies. I know you've discussed this before, and I did search for it, but I couldn't find what I was looking for. If you don't want to repeat yourselves, could you please point me to the pertinent thread? Do you need to remove and clean up both the interior and the underhood sides of the connector in order to clean it properly? Thanks a lot.