Filling the nipples sounds like a bad idea to me.. you pretty much have to dismount the tyre, remove all the sealant whatever you use and then redo the whole sealing process if you want to be sure that no leaks develop when you have to adjust the spokes?
I saw a method earlier about a kind of tape to be used to seal the rim. Tape would be easier to remove and allows for adjustment of the spokes. Anybody know if any of the tapes which I could get from the hardware store could do this trick? Or maybe use some kind of film over a strong glue of sorts, similar to using a silicone layer evened with a spatula?
Great write up nevertheless!