Originally Posted by neil0502
Spoke threads and spoke holes in the rim should generally be lubricated with light grease or oil to allow the nipples to turn freely enough to get the spokes really tight. This is less important than it used to be ... only the right side spokes and spoke holes need to be lubricated...
I disagree with some fine points here ... all threaded fasteners (including spokes) should be lubricated for consistency of turning and corrosion prevention. Also, the surface where the nipple and rim make contact should be lubed for the same reason. Whether you use oil or grease doesn't matter, and I can't speak to the original question about spoke prep, cause I have not used it. But I have 20-odd-year-old wheels that I can still true (galvanized and stainless), built with greased threads.
3 in 1 has probably changed formulas, but it used to be vegetable based and subject to getting gummy and useless from oxidation, so it should never be used on anything that you expect to continue to function for more than a few weeks.