All my unglazed pots are polished. These yohen pots fired in the firebox need the most work.
First, I use a a stone (half a sharpening stone Sicarbide) Mostly on the foot, but for any big stuff on the pot
Then I use coarser then fine sandpaper.
then 3M green scrubbie wet.
then a sheepskin buffer on my mixing drill
I learned this method during my apprenticeship at Shimaoka's. Traditionally, they used ricestraw instead of 3M pads, but they switched to the 3M pads. Also, they don't use a buffer, but instead, an appentice can polish a yohen pot for a full day with a cotton cloth. The buffer is my apprentice and it gets the job done in about 15 minutes.