Yes, they can be re-chromed.
As far as cleaning them up...I have used everything. The best I can do is make dull....shiny-dull.
Any of the liquid chrome polishes, as far as they go I have noticed no difference between $ and $$$.
On another note (not highjacking) if you need chrome 1-piece lug nuts, Autozone actually has them. They are almost exactly like the factory ones...for less.