It is not generally a favoured process any more...most people like to keep their parts with the OG finish these days. Many a good part has been ruined by over polishing. A lot of people like the survivor look these days and buy parts accordingly, But......if you still want to go down this route the thing to do would be to remove the old powdercoat/ paint with paint stripper. Nitromors is not generally regarded with being any good these days but I have never had problems with it....just follow instructions.
Once all the powdercoat has been removed it's up to you what you do. You can either lightly polish with metal polish or if you want the mirror like show bike look you will need more work.....
You will need to work up the grades with wet n dry paper....I would start with something like 320 and remove all the casting marks/ imperfections. then work up the grades removing all the scratches the last grade left til you finish it with 1200 or 1500 grit. You should be left with very flat shiny metal which almost looks polished. Once you are happy with it use metal polish like Autosol and a rag to finish it off. On such a small item it should be easy enough to do by hand. will take a few hours and plenty of elbow grease. the longest part is the sanding, once you have prepared the metal it doesn't take long to polish it. It may take a few goes with the polish before its mirror like and you will need to have got in the nooks and crannies with the wet n dry to achieve a nice finish. The beauty of doing it by hand is that you have control and hopefully won't polish out your lettering!
hope this helps
D
