wouldn't use anything to aggressive on them just incase - mind you i sanded my red ones down using progressively finer grades of wet and dry until i got to 2000 grit.
I then did the soak trick and lastly bought some of the red coloured car polish from halfords and went to work on them with that - lastly covered them again in wd40 and buffed to a nice shine. the difference was night and day - i seriously considered throwing them away when they 1st arrived as they were in a right proper state
Heres a pic of how they turned out - was only really a few hours work in total over 2 days.
(http://www.radbmx.co.uk/archive/albums/z164/wildwood1971/SN850108.jpg)
(http://www.radbmx.co.uk/archive/albums/z164/wildwood1971/SN850115.jpg)