My 2nd ever post in this forum.
This guy shows how to do it, even using the trombone cleaner, which I think he found from PaulE on this forum!
https://youtu.be/Hz-C9pkMnDk
I just learned the lesson the hard way. A 986 I bought last week had clogged drains, including the one in the frunk, which then allowed the battery area to fill up with water, and the place where the battery cable connects to the firewall rusted out and broke. That connection was to something called the "power distribution box," which I discovered is not available in the U.S. Had to get it from Germany. 3 week wait and $700.
Lesson: keep them holes clean!