New zincs on the transom, the rudder, and the bow and stern thrusters, a good pressure washing, another coat of bottom paint on the hull, and a coat of antifouling paint on the running gear:
I hate not being to watch all the fun in person, but Herve at Nordic NW took some photos for me so I could see the progress.
Here's the running gear before antifouling paint:
And here's one of the thruster zincs (clearly in need of replacement):
So…zincs! For you non-boat people, here's the deal: Zincs are also called galvanic anodes, or sacrificial anodes, and these anodes are used to protect submerged metal structures from corrosion. They're made from a metal with a more active voltage than the metal of the submerged structure. This difference in potential between the two metals means that the zinc corrodes first so that the thing you care about does not, hence, the name "sacrificial anode."
Too bad these won't work on an Airstream to combat that blasted filiform corrosion, isn't it??