My spokes looked like that too - no pitting but oxidized galvanized steel - old and dull.
I just recently did a wet sanding with 400 grit paper, this took everyting off quickly and made them clean & shiny. Then I buffed them hard up and down each spoke with #000 steel wool to make them smooth and now they look factory new! At this point, you could even use a polish as mentioned above(I'm going to now) and they will sparkle.