Polishing is an issue that comes up often on the pen discussion boards. My own practices have changed and become more conservative over the years. Unless there are scratches to be removed or oxidation to be ameliorated I don’t use polish at all. A good, thorough rub with a soft cloth is enough for most materials. Hard rubber responds especially well, as does celluloid and casein. My modern pens – mostly eighties and nineties Japanese pens – are probably acrylic, I should think, and they polish up very easily in the same way. Metal parts do need some actual polish to look their best. I use Simichrome, very sparingly.
When there are scratches to reduce or oxidation on hard rubber I use the three-part Novus abrasive polish. This is a tool like any other and should be used in the way intended; beginning with the No 3 coarse scratch remover, going on to the No 2 and finishing with No 1. Used in that way it is very effective, restoring old pens to something approaching their original appearance without falling into the trap of producing an unnatural glaring shine on a buffing machine. I have tried other polishes over the years but I only use Novus now as it has the reputation of being harmless to the materials I work with. I hope that’s true. I’m not a chemist and I have to go by the experience of other restorers as well as my own. As I said above, most of the pens I restore don’t have any chemical polishes applied to them at all apart from a little metal polish.
In the same vein of trying to avoid harm, I never use wax of any kind. Even pure beeswax is hard to remove and will provide a coating that prevents the escape of any gases produced, to the detriment of the materials. Other waxes such as the popular Renaissance Wax are said by those who know better than me to contain chemicals that may be harmful to the materials pens are made from.
I have always restored conservatively. More and more I subscribe to the advice, “first do no harm.”