Removing any imperfections from the casting process 1st stage polishing with rough grit sand paper.
Scratches are nothing more than deep uneaven surface. The first step to polishing is to make sure the surface is even out. Use rough sand paper and gradually use finer sand paper. There are 2 ways to get rid of scratched, fill the deep scratches and sand it to match the surrounding surface so that its level or sand the surrounding surface and level it to match the depth of the scratches with a suitable grit and gradually use finer sand paper.
Use a concave file to roughly remove ant access plastic try not to press to hard and scratch any smooth surface. After that start sanding using a rough sand paper nothing more than 1500 grit, remember not to use too much pressure, i will be using automotive body work grade sand paper, just place the sand paper on the surface and sand. After all surface has been sand, start wet sanding using the same grit (1500 grit).
Wet sanding will result in a finer and smoother surface compared to dry sanding. The goal is to make sure all surface is evenly smooth, in some cases you may find small patches still un-sand, these are deep dents on the surface and you may need to attack it from different angles. You can start with a finer 2000 grit, but this will result in more time spent getting rid of the rough edges. Spend more time wet sanding usind the 2000 grit, wet sanding wil also help spotting uneven surfaces.
The steps are simple:-
-File access plastic with file ( for removing large access plastic )
-1500 grit dry sand > 1500 grit wet sand ( for removing and even out the surface )
-2000 grit dry sanding > 2000 grit wet sanding ( fine tune the surface for smoother result )
The most important thing to remember is not to get carried away or apply to much pressure. Sand paper eats plastic, so try not to sand the same spot for too long, you may end up with an uneven flat spot. You have only one chance to get it right. The motive is to gradually smoothen the surface. There are 3 parts that need polishing the grill housing, transducer bracket and the L/R plastic on the headband.