When you want to polish something. You need to confirm or make a choice for the below things.
#1 Confirm the material of the workpiece, soft metal, hard metal, stainless steel or aluminum etc. The material will determine your choice of buffing wheel and polishing compound.
#2 Check the surface status of the workpiece, with scratches, marks or dirt. This will determine do you need a sanding process before polishing. If the workpiece with marks or heavy scratches, please use abrasive products to sand it before polishing.
#3 According to your polishing purpose select the proper buffing wheel and polishing compound.
The following picture will tell you how to choose a polishing wheel and polishing compound when polishing different material objects.