Insight, a professional restorer would use both mechanical and chemical treatments depending upon what is found. This, in order to ensure the surface is stripped absolutely clean. Otherwise, there could be failure in the re-patination process resulting in an ununiformed finish. One shakudo tsuba I had professionally restored took five (tedious, careful, time consuming) mechanical cleanings before being chemically prepared for re-patination.
Even then the success of the re-patination will depend upon the quality of the shakudo. Which to some extent will be an unknown factor. Eventually, the quality of the shakudo will become apparent in the final result. On an excellent shakudo tsuba the finish will continue to re-patinate and improve, even dramatically, over time.
With this wave tsuba, not only is there the body to restore but the rim needs attention, too. Then there is the question of what to do about all of the silver? and/or gold? drops that are missing?
Value? Worth restoring? Kantei gives an answer.
Good luck.