This is how I polish up yoyo.

1. Mount yoyo on lathe or drill and spin.
2. If you have any dents or marks you want to take out, start sanding with 150.
3. Move to 250 grit, then to 400 grit (wet), 600 grit (wet), 1000 grit (wet).
4. After that you use pumice powder. Dampen a cloth or paper towel and put a little bit of pumice powder on it, and polish with that for a while. Clean yoyo off when done.
5. Do step 4 with rotten stone powder instead of pumice.
6. If you are polishing metal you can skip steps 4 and 5 and go straight to your semi chrome polish. Put some of the polish cream onto a cloth or paper towel and buff your metal with it.

Note: If you want to polish a yoyo that is both plastic and metal, polish one at a time. If you don't you will melt small pieces of aluminum into the plastic.

Note: If you are just looking to sand a yoyo for better grinding use 150 grit sand paper or a bit finer.