cutting compound, plenty of water and an old towel. unless the surface of the lights is very opaque you dont need to wet sand them. takes about 30 minutes per headlight on a ducato. i did this to the lights on my last van before selling and it made a big difference
U use Farecla g3 compound and a 2.5" polishing head on a drill, I know you said preferably no still but it is hard work done by hand. Once polished i give the lenses a coat or two of clear acrylic lacquer from a rattle can, this stops them going yellow again too quickly.