I know someone who does a very good job at removing gutter rash.
He did my rims, but I warn you its not cheap.
Powdercoating is around $50 a rim I think.
Machining the rims will cost a bit, im not too sure on the figure of just the maching, as I got them polished/painted at the same time.
If your getting new school style rims, just get them new. Atleast then you know what your getting.
I would only bother with these types of services if the wheel style and offset/size is quite rare and only available second hand.
This is a pic of some wheels that a place in SA touched up for me, keep in mind these rims are probably about 15 years old now: