Originally Posted by
oneclick
Bung a cork in the top of any hollow ones.
And yes, seatpost flutes are a Completely Stupid Idea.
I won't argue that but they do dress a vintage bike up a bit. When I put the white lithium grease on my fluted seat posts I always make sure there is enough in the flutes to seal them at the top of the seat tube. Wipe the excess off flush to the seat tube using a Q-tip in the flutes and no moisture can get down the flutes.
A little clear nail polish applied around the cable housing at the openings for through the frame cables would help seal them against moisture. I also plug any unused threaded frame holes with stainless steel set screws and then seal them with clear nail polish to keep them from backing out and to keep moisture from seeping in around the threads. Probably overkill but it makes me feel better LOL.