Simple bulk jewelry piece cleaning/re-finishing

I have many pieces of metal cufflinks which are "dirty" with a greasy white residue over them. I am not sure exactly this residue is, but I am fairly certain that it can be cleaned off with some sort of industrial cleaning solution. I need someone who is knowledgeable about this type of thing and who will be able to clean these pieces for me. I purchased these items in bulk from China and about 25% of the items that I received had this problem. Each piece is very small, less than an inch long and weighing a fraction of an ounce. The material of each cufflink is brass with some sort of chrome/metallic finish. Rubbing the dirty face of a piece only clears up the metal for a second; the white residue quickly returns to the surface. I have approximately 1,100 pieces that need to be cleaned. Every piece is identical. If I award you the project, I will mail you 10-20 sample pieces, which you will clean and mail back to me. Once it is apparent that you are able to clean the pieces, I will send all the remaining pieces and will pay once they have been sent back. I have attached pictures of a dirty vs. clean item, so you can see what the issue is. Also, I have attached a photo of the disassembled jewelry piece. This white residue is primarily only an issue on the front round "face" of the cufflink pieces. The pieces should not be damaged during the cleaning process. - You must demonstrate to me your knowledge of this problem and tell me how you will clean the jewelry. - You must be capable of handling the entire workload and have a reasonable turnaround time. - You should preferably be based in the United States for quicker turnaround time.