Should I lubricate rear derailleur wheels
Usually if they're turning as you describe with high resistance, they're either gunked up and need cleaning or they're put together wrong. They should spin very freely without any added lubrication. Grease would probably tend to do as you say and attract dirt, but a thin coating on the outside of the bushing isn't going to ruin anything if you want to try it. I do a drop of light lube at the gap of each one to keep them running quietly, but it's usually a negligible difference either way.