Given what you wish to accomplish, the technique of TUMBLING comes to 
mind.  In your case, the inside of the vessel is the final product, but 
methods are methods.

If you look towards jewelry making or polishing of small parts, the 
methods and sanding materials are all explained.

The product that does the work is usually something akin to ball 
bearings.  Put them inside the orb with a polishing product and tumble 
for days.

Frank