Jim, welcome to the R-390 world. There's lot's of info available online about our toys. This is the 'pearls', which has info on the 390 line of rx's (mostly the 390A). There's 2 items about refinishing:
http://www.r-390a.net/Pearls/
There's a lot more on the web - just google R-390 or R-390A, etc.
Regards, Larry