I offer Japanese sword polishing services and I buy swords and entire collections. I take pride in the fact that I only use traditional methods to restore swords, I do not use chemicals or improper methods to polish Nihon-to, there is only one way, the proper way.
Don't be fooled by the recent trend of acid polishing on Nihon-to, it damages swords and it is only the polishers trick to do the work quickly.